Without a lot of work, I think you could treat the @mention as a way to give priority to comments. For example, if I’m following a task, I will see the comment in my inbox, whether it’s really for me or not. But if someone @mentions me, that’s more of a direct, “hey you! work on this,” type message. But it’s not treated any different than a normal message that would show up in my inbox.
Maybe a focus on my @mentions or maybe a second box that only lists the stuff where I’m mentioned. Something like that.