There is a broken markdown link when you click the "Mod" link on a user's meta profile:
The one for "Contact user privately" works fine:
Note that the latter links to
https://codegolf.stackexchange.com/users/message/create/<USERID>; I don't know if that has anything to do with it. In case it's relevant, the link in the broken part has dashes in it (that is, the username contains spaces).