"@dang" doesnt do anything. email him if you want his attention.
Honestly at this point, it should, as it is widely used. Maybe a page where be can see all the mentions so he can check them if he has time, not something disruptive like an email notification for every mention obviously.
Yes, no way that can go wrong
There's a lot of things that are standard features that aren't here - the lack of @'ing, notifications, followers, etc are all things I like about HN.
While there’s probably no backend functionality, I would bet he has a feed set up to find comments containing the phrase “dang”.