[quote=@Captain Jordan]
As an experiment, you should try dropping the brackets on @mention, at least for simple usernames. It'll probably require the username-feeding system or brackets for more complex usernames (with fancy characters like space or '), but for for a mention like @Mahz. 
[/quote]
The brackets essentially keep the parser super simple, so I think you're right: A good middleground would be for an auto-suggestion box to appear once you've typed an "@" symbol and then one character, and then choosing a name from its drop-down will inject the bracketed version for you.

This makes it nicer to mention people, prevents typos, yet keeps the parser simple (unchanged). Though the few methods I can think of for making an auto-suggestion box appear while you're writing a post are still complex enough for me to put this kind of polish on ice til I tackle some richer features.

It'd be helpful if post updates could send new notifications (up until a threshold is hit), but I haven't put much thought into how to constrain it from resending notifications. I know what I'll do: I'll change the notifications system so that notifications aren't deleted from the database, just "seen". That way I know how many notifications each post has generated (threshold detection), which users have already been notified, and a nice side-effect is that I can add a "See old notifications" button to the notifications page which can sometimes be useful.