[Morrus]

OK, ignore the above - it works on 3.8.4.

It's a fantastic system! I've nominated it for MOTM and purchased the Pro version; this is a really good idea. There are a couple of oddities (such as only counting the first mention in a post, so if you mention more than one person it doesn't appear in the Mentions tab on their profile), and the Statistics page seems to confuse mentions and tags (someone is listed as top tag when all he has done is mention, for example), but I'm sure these will get ironed out.

Also, the option to not show the @ in the Admin CP resets to "Yes" every time you save the settings, and if you put the tag box below the thread it simply disappears.

And an option for users to opt-out would be great; I've had a couple complain about being bugged by thread mentions when they're not interested in following them.