@jon The first can be problematic if there is an account on your server (and it could happen) that has same username but it is a totally different person, it mentions a wrong person then.

The latter is... I dunno how can I type that character on my keyboard. But as others said: I consider this as an email address. In emails I mention the full email address to ensure the recipient(s) can reach the mentioned person.

So, for me, it will stay @hron84@twitter.com forever.