Frankly speaking, this @ system with punching in usernames is extremely uncomfortable when XF is used in different languages. Because we always have to switch to English, then choose uppercase, then write in username (that could also require switching between languages). Some nicknames are long or gibberish, contain numbers, etc. All that is way too complicated to compare with just one click. Click username to reply would be a splendid addition to usability.
I am looking forward to find this option in XF, if available. Or, if anyone knows a good working add-on that does this trick, I would really appreciate a link.