Currently, when you reply to a post in a thread by clicking the Reply link on that post, it inserts the username into the editor and puts the cursor before the username. In my opinion, and this may just be because I'm using to the way mentions work on Twitter, I think the cursor should be automatically placed with a space after the username, like this:

as opposed to this, the way it currently works (although it does add a space at the end of the username):

With the way it currently works, I press the End key on my keyboard and I'm fine, but I think it would be nice if the cursor just started there anyway. Might just be me, though.