diff --git a/app/assets/javascripts/discourse/dialects/category_hashtag_dialect.js b/app/assets/javascripts/discourse/dialects/category_hashtag_dialect.js
index 1ea3052b8eb..4beb7ab537e 100644
--- a/app/assets/javascripts/discourse/dialects/category_hashtag_dialect.js
+++ b/app/assets/javascripts/discourse/dialects/category_hashtag_dialect.js
@@ -4,7 +4,7 @@
 **/
 Discourse.Dialect.inlineRegexp({
   start: '#',
-  matcher: /^#([\w-]{1,50})/,
+  matcher: /^#([\w-]{1,50})/i,
   spaceOrTagBoundary: true,
 
   emitter: function(matches) {
diff --git a/app/assets/javascripts/discourse/dialects/mention_dialect.js b/app/assets/javascripts/discourse/dialects/mention_dialect.js
index 1641c309439..3848ae1503b 100644
--- a/app/assets/javascripts/discourse/dialects/mention_dialect.js
+++ b/app/assets/javascripts/discourse/dialects/mention_dialect.js
@@ -7,11 +7,11 @@ Discourse.Dialect.inlineRegexp({
   start: '@',
   // NOTE: since we can't use SiteSettings here (they loads later in process)
   // we are being less strict to account for more cases than allowed
-  matcher: /^@([\w.-]+)/,
+  matcher: /^@(\w[\w.-]{0,59})\b/i,
   wordBoundary: true,
 
   emitter: function(matches) {
-    var mention = matches[0],
+    var mention = matches[0].trim(),
         name = matches[1],
         mentionLookup = this.dialect.options.mentionLookup;
 
diff --git a/app/models/username_validator.rb b/app/models/username_validator.rb
index 891958b169b..e0ba6cfacb7 100644
--- a/app/models/username_validator.rb
+++ b/app/models/username_validator.rb
@@ -61,21 +61,21 @@ class UsernameValidator
 
   def username_char_valid?
     return unless errors.empty?
-    if username =~ /[^A-Za-z0-9_\.\-]/
+    if username =~ /[^\w.-]/
       self.errors << I18n.t(:'user.username.characters')
     end
   end
 
   def username_first_char_valid?
     return unless errors.empty?
-    if username[0] =~ /[^A-Za-z0-9_]/
+    if username[0] =~ /[^\w]/
       self.errors << I18n.t(:'user.username.must_begin_with_alphanumeric')
     end
   end
 
   def username_last_char_valid?
     return unless errors.empty?
-    if username[-1] =~ /[^A-Za-z0-9_]/
+    if username[-1] =~ /[^\w]/
       self.errors << I18n.t(:'user.username.must_end_with_alphanumeric')
     end
   end