diff --git a/default.yaml b/default.yaml
index ea1e5029..26d41611 100644
--- a/default.yaml
+++ b/default.yaml
@@ -143,6 +143,14 @@ server:
     # problematic.
     casemapping: "ascii"
 
+    # allowed-characters provides fine-grained control over allowable characters in identifiers
+    # (nicknames, account names, and channel names):
+    # allowed-characters:
+        # allow IRC formatting/control characters (bold, color, italics, underline, etc.)
+        # irc-formatting: false
+        # allow printable Unicode glyphs (emoji, symbols, combining marks, legacy computing, block elements)
+        # printable-glyphs: false
+
     # enforce-utf8 controls whether the server will preemptively discard non-UTF8
     # messages (since they cannot be relayed to websocket clients), or will allow
     # them and relay them to non-websocket clients (as in traditional IRC).
diff --git a/irc/client_lookup_set.go b/irc/client_lookup_set.go
index 6e028206..7007db6b 100644
--- a/irc/client_lookup_set.go
+++ b/irc/client_lookup_set.go
@@ -8,6 +8,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/ergochat/irc-go/ircfmt"
+
 	"github.com/ergochat/ergo/irc/caps"
 	"github.com/ergochat/ergo/irc/modes"
 	"github.com/ergochat/ergo/irc/utils"
@@ -99,11 +101,15 @@ func (clients *ClientManager) SetNick(client *Client, session *Session, newNick
 	// these restrictions have grandfather exceptions for nicknames registered
 	// on previous versions of Ergo:
 	if newNick != accountName {
+		plainNick := newNick
+		if globalAllowedCharacters.IRCFormatting {
+			plainNick = ircfmt.Strip(newNick)
+		}
 		// can't contain "disfavored" characters like <, or start with a $ because
 		// it collides with the massmessage mask syntax. '0' conflicts with the use of 0
 		// as a placeholder in WHOX (#1896):
-		if strings.ContainsAny(newNick, disfavoredNameCharacters) || strings.HasPrefix(newNick, "$") ||
-			newNick == "0" {
+		if strings.ContainsAny(newNick, disfavoredNameCharacters) || strings.HasPrefix(plainNick, "$") ||
+			plainNick == "0" {
 			return "", errNicknameInvalid, false
 		}
 	}
diff --git a/irc/config.go b/irc/config.go
index 7a149491..c8d2e35d 100644
--- a/irc/config.go
+++ b/irc/config.go
@@ -626,14 +626,15 @@ type Config struct {
 		supportedCapsWithoutSTS  *caps.Set
 		capValues                caps.Values
 		Casemapping              i18n.Casemapping
-		EnforceUtf8              bool                `yaml:"enforce-utf8"`
-		OutputPath               string              `yaml:"output-path"`
-		IPCheckScript            IPCheckScriptConfig `yaml:"ip-check-script"`
-		OverrideServicesHostname string              `yaml:"override-services-hostname"`
-		MaxLineLen               int                 `yaml:"max-line-len"`
-		SuppressLusers           bool                `yaml:"suppress-lusers"`
-		AdditionalISupport       map[string]string   `yaml:"additional-isupport"`
-		CommandAliases           map[string]string   `yaml:"command-aliases"`
+		AllowedCharacters        AllowedCharactersConfig `yaml:"allowed-characters"`
+		EnforceUtf8              bool                    `yaml:"enforce-utf8"`
+		OutputPath               string                  `yaml:"output-path"`
+		IPCheckScript            IPCheckScriptConfig     `yaml:"ip-check-script"`
+		OverrideServicesHostname string                  `yaml:"override-services-hostname"`
+		MaxLineLen               int                     `yaml:"max-line-len"`
+		SuppressLusers           bool                    `yaml:"suppress-lusers"`
+		AdditionalISupport       map[string]string       `yaml:"additional-isupport"`
+		CommandAliases           map[string]string       `yaml:"command-aliases"`
 	}
 
 	API struct {
@@ -1426,8 +1427,8 @@ func LoadConfig(filename string) (config *Config, err error) {
 	}
 
 	if !i18n.Enabled {
-		if config.Server.Casemapping != i18n.CasemappingASCII {
-			return nil, fmt.Errorf("i18n support was compiled out; set casemapping to 'ascii' or recompile")
+		if config.Server.Casemapping != i18n.CasemappingASCII || config.Server.AllowedCharacters.PrintableGlyphs {
+			return nil, fmt.Errorf("i18n support was compiled out; set casemapping to 'ascii' and printable-glyphs to false, or recompile")
 		}
 	}
 
diff --git a/irc/i18n/strings.go b/irc/i18n/strings.go
index 400dc805..09c2c74b 100644
--- a/irc/i18n/strings.go
+++ b/irc/i18n/strings.go
@@ -28,7 +28,7 @@ const (
 var (
 	// reviving the old ergonomadic nickname regex:
 	// in permissive mode, allow arbitrary letters, numbers, punctuation, and symbols
-	permissiveCharsRegex = regexp.MustCompile(`^[\pL\pN\pP\pS]*$`)
+	permissiveCharsRegex = regexp.MustCompile(`^[\pL\pN\pP\pS\pM]*$`)
 )
 
 // String Errors
diff --git a/irc/server.go b/irc/server.go
index 823a98a8..a2f37573 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -719,6 +719,7 @@ func (server *Server) applyConfig(config *Config) (err error) {
 		server.nameCasefolded = config.Server.nameCasefolded
 		globalCasemappingSetting = config.Server.Casemapping
 		globalUtf8EnforcementSetting = config.Server.EnforceUtf8
+		globalAllowedCharacters = config.Server.AllowedCharacters
 		MaxLineLen = config.Server.MaxLineLen
 		RegisterTimeout = config.Server.IdleTimeouts.Registration
 		PingTimeout = config.Server.IdleTimeouts.Ping
@@ -733,6 +734,8 @@ func (server *Server) applyConfig(config *Config) (err error) {
 			return fmt.Errorf("Casemapping cannot be changed after launching the server, rehash aborted")
 		} else if globalUtf8EnforcementSetting != config.Server.EnforceUtf8 {
 			return fmt.Errorf("UTF-8 enforcement cannot be changed after launching the server, rehash aborted")
+		} else if oldConfig.Server.AllowedCharacters != config.Server.AllowedCharacters {
+			return fmt.Errorf("Cannot change allowed-characters after launching the server, rehash aborted")
 		} else if oldConfig.Accounts.Multiclient.AlwaysOn != config.Accounts.Multiclient.AlwaysOn {
 			return fmt.Errorf("Default always-on setting cannot be changed after launching the server, rehash aborted")
 		} else if oldConfig.Server.Relaymsg.Enabled != config.Server.Relaymsg.Enabled {
diff --git a/irc/strings.go b/irc/strings.go
index e227cb8f..dc8451b7 100644
--- a/irc/strings.go
+++ b/irc/strings.go
@@ -9,6 +9,8 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/ergochat/irc-go/ircfmt"
+
 	"github.com/ergochat/ergo/irc/i18n"
 	"github.com/ergochat/ergo/irc/utils"
 )
@@ -32,6 +34,29 @@ const (
 	disfavoredNameCharacters = `<>'";#`
 )
 
+type AllowedCharactersConfig struct {
+	IRCFormatting   bool `yaml:"irc-formatting"`
+	PrintableGlyphs bool `yaml:"printable-glyphs"`
+}
+
+var globalAllowedCharacters AllowedCharactersConfig
+
+func containsDisallowedControlChars(str string, allowIRCFormatting bool) bool {
+	for i := 0; i < len(str); i++ {
+		b := str[i]
+		if b < 32 || b == 127 {
+			if allowIRCFormatting {
+				switch b {
+				case 0x02, 0x03, 0x04, 0x0F, 0x11, 0x16, 0x1D, 0x1E, 0x1F:
+					continue
+				}
+			}
+			return true
+		}
+	}
+	return false
+}
+
 // XXX this is a global variable without explicit synchronization.
 // it gets set during the initial Server.applyConfig and cannot be changed by rehash:
 // this happens-before all IRC connections and all casefolding operations.
@@ -45,7 +70,14 @@ var globalUtf8EnforcementSetting bool
 
 // Casefold returns a casefolded string, without doing any name or channel character checks.
 func Casefold(str string) (string, error) {
-	return i18n.CasefoldWithSetting(str, globalCasemappingSetting)
+	if globalAllowedCharacters.IRCFormatting {
+		str = ircfmt.Strip(str)
+	}
+	res, err := i18n.CasefoldWithSetting(str, globalCasemappingSetting)
+	if err != nil && globalAllowedCharacters.PrintableGlyphs {
+		res, err = i18n.CasefoldWithSetting(str, i18n.CasemappingPermissive)
+	}
+	return res, err
 }
 
 // CasefoldChannel returns a casefolded version of a channel name.
@@ -82,6 +114,10 @@ func CasefoldChannel(name string) (string, error) {
 
 // CasefoldName returns a casefolded version of a nick/user name.
 func CasefoldName(name string) (string, error) {
+	if containsDisallowedControlChars(name, globalAllowedCharacters.IRCFormatting) {
+		return "", errInvalidCharacter
+	}
+
 	lowered, err := Casefold(name)
 
 	if err != nil {
@@ -140,6 +176,9 @@ func isIdent(name string) bool {
 // Skeleton produces a canonicalized identifier that tries to catch
 // homoglyphic / confusable identifiers.
 func Skeleton(name string) (string, error) {
+	if globalAllowedCharacters.IRCFormatting {
+		name = ircfmt.Strip(name)
+	}
 	switch globalCasemappingSetting {
 	default:
 		return i18n.Skeleton(name)
diff --git a/irc/strings_test.go b/irc/strings_test.go
index 537e55f5..7422847a 100644
--- a/irc/strings_test.go
+++ b/irc/strings_test.go
@@ -220,3 +220,91 @@ func TestCanonicalizeMaskWildcard(t *testing.T) {
 		tester("РОТАТО!Potato", "ротато!potato@*", nil)
 	}
 }
+
+func TestAllowedCharactersIRCFormatting(t *testing.T) {
+	oldAllowed := globalAllowedCharacters
+	t.Cleanup(func() {
+		globalAllowedCharacters = oldAllowed
+	})
+
+	globalAllowedCharacters = AllowedCharactersConfig{
+		IRCFormatting: true,
+	}
+
+	testCases := []struct {
+		input  string
+		folded string
+		err    bool
+	}{
+		{"\x02bold\x02", "bold", false},
+		{"\x0304,01red\x0f", "red", false},
+		{"\x1ditalic\x1d", "italic", false},
+		{"\x1funderline\x1f", "underline", false},
+		{"\x16reverse\x16", "reverse", false},
+		{"\x11monospace\x11", "monospace", false},
+		{"\x1estrike\x1e", "strike", false},
+		{"\x02\x0304Mixed\x0f\x02", "mixed", false},
+		// only formatting codes, no text -> empty string error
+		{"\x02\x02", "", true},
+		{"\x0304\x0f", "", true},
+		// disallowed control characters
+		{"\x07bell", "", true},
+		{"\x1bescape", "", true},
+		{"tab\tcharacter", "", true},
+		{"null\x00byte", "", true},
+	}
+
+	for _, tt := range testCases {
+		res, err := CasefoldName(tt.input)
+		if tt.err && err == nil {
+			t.Errorf("expected error for [%q], got nil", tt.input)
+		} else if !tt.err && err != nil {
+			t.Errorf("unexpected error for [%q]: %v", tt.input, err)
+		} else if !tt.err && res != tt.folded {
+			t.Errorf("expected [%q] to fold to [%q], got [%q]", tt.input, tt.folded, res)
+		}
+	}
+}
+
+func TestAllowedCharactersPrintableGlyphs(t *testing.T) {
+	if !i18n.Enabled {
+		t.Skip("i18n not enabled")
+	}
+
+	oldAllowed := globalAllowedCharacters
+	t.Cleanup(func() {
+		globalAllowedCharacters = oldAllowed
+	})
+
+	globalAllowedCharacters = AllowedCharactersConfig{
+		PrintableGlyphs: true,
+	}
+
+	testCases := []struct {
+		input  string
+		folded string
+		err    bool
+	}{
+		// Block elements
+		{"█Block█", "█block█", false},
+		{"░Shade░", "░shade░", false},
+		// Legacy computing (U+1FB00)
+		{"\U0001FB00Legacy\U0001FB00", "\U0001fb00legacy\U0001fb00", false},
+		// Emojis & Symbols
+		{"👾gamer👾", "👾gamer👾", false},
+		{"🔥Fire🔥", "🔥fire🔥", false},
+		// Combining marks
+		{"e\u0301clair", "éclair", false},
+	}
+
+	for _, tt := range testCases {
+		res, err := CasefoldName(tt.input)
+		if tt.err && err == nil {
+			t.Errorf("expected error for [%q], got nil", tt.input)
+		} else if !tt.err && err != nil {
+			t.Errorf("unexpected error for [%q]: %v", tt.input, err)
+		} else if !tt.err && res != tt.folded {
+			t.Errorf("expected [%q] to fold to [%q], got [%q]", tt.input, tt.folded, res)
+		}
+	}
+}
diff --git a/traditional.yaml b/traditional.yaml
index 8b9c396d..2eba6146 100644
--- a/traditional.yaml
+++ b/traditional.yaml
@@ -117,6 +117,14 @@ server:
     # problematic.
     casemapping: "ascii"
 
+    # allowed-characters provides fine-grained control over allowable characters in identifiers
+    # (nicknames, account names, and channel names):
+    # allowed-characters:
+        # allow IRC formatting/control characters (bold, color, italics, underline, etc.)
+        # irc-formatting: false
+        # allow printable Unicode glyphs (emoji, symbols, combining marks, legacy computing, block elements)
+        # printable-glyphs: false
+
     # enforce-utf8 controls whether the server will preemptively discard non-UTF8
     # messages (since they cannot be relayed to websocket clients), or will allow
     # them and relay them to non-websocket clients (as in traditional IRC).