I do this kind of thing all the time:
In addition to moving these declarations closer to where you use them as @lokiastari said, the initializations are pointless because you overwrite them anyway.
That is, when I mention a user, I don't just mention their (uhm, slightly mispelled) name, I link to their profile. Not really to drive people to his profile page (though hey, why not), but because he might change his nick and invalidate my post. Using a link should survive such events, based on the observation that these links all go to the same page:
Actually, just like SE changes post links to their title automatically, it could probably change user profile links to their proper @nick, whatever its current value.
But what I would really like is be able to enter an @ mark and use autocompletion to select any user involved in the discussion (posted question / answer / comment), similar to the way it works in comments.
In case you're wondering, I rarely want to link to a comment, because comments can be deleted. If user X suggested an improvement to my post, I usually update my post accordingly and credit the user. Once his comment is part of my post, it makes sense for him to delete the comment. And in any case, since I already credit him in the post, the clickable link to the comment is pointless anyway when there's no new information there. Linking to other answers might be a slightly different matter. But in any case, crediting another user deserves a proper link to his profile, and it would be great if this was easier to do than it is today.