No way that I know of currently. I am pretty sure it is possible via some add-on code for the forum software. This is a feature I have thought about myself on occasion.
Like on facebook where you mention someones name and it links to them and also notifies them that they've been tagged.
Theres only been a few times where I wanted to tag someone but Im sure Im not the only person. It would be nice but not a big deal.
I looked all through the software and cannot find a "tagging" option. I will contact Xenforo this weekend and ask them if that option can be installed.....
I don't know that I would use it much, but there's been a few times I've wanted to tag Pete or Walker in a new thread.
Thanks Scotty I wouldnt worry about it to much it would be nice to have but like others have said might not get to much use.