I approve this idea c: The only major flaw I see is who would be tagged and notified. Like when sending someone a PM on this website, it might not go to the same person if they have the same username as someone else. I'm not sure how exactly that could be fixed, but otherwise I love this idea. I hope the staff will at least consider the idea, I think it could be pretty helpful.
Hmmm. I was searching the boards to find a topic related to tagging before posting a thread myself, and couldn't quite find one, so I did so. I apologize for the tiny mistake in not seeing this. Though, carrying on from this thread instead, I really do think this would be a quality feature to have on these Forums. They would be handy to people in many ways, so long as they know of ways to use them.