more flexible regex for quick mentions, reported by dirk

fun.go

@@ -27,6 +27,7 @@ import (
 	"regexp"
 	"strings"
 	"time"
+	"unicode"
 
 	"golang.org/x/net/html"
 	"humungus.tedunangst.com/r/webs/cache"
@@ -457,7 +458,8 @@ func memetize(honk *Honk) {
 	honk.Noise = re_memes.ReplaceAllStringFunc(honk.Noise, repl)
 }
 
-var re_quickmention = regexp.MustCompile("(^|[ \n])@[[:alnum:]]+([ \n.]|$)")
+// be mindful not to match trailing @
+var re_quickmention = regexp.MustCompile("(^|[ \n])@[[:alnum:]]+([ \n.,']|$)")
 
 func quickrename(s string, userid int64) string {
 	nonstop := true
@@ -472,7 +474,7 @@ func quickrename(s string, userid int64) string {
 			prefix += "@"
 			m = m[1:]
 			tail := ""
-			if last := m[len(m)-1]; last == ' ' || last == '\n' || last == '.' {
+			if last := m[len(m)-1]; last == ' ' || last == '\n' || unicode.IsPunct(rune(last)) {
 				tail = m[len(m)-1:]
 				m = m[:len(m)-1]
 			}