Maybe it just does a random check on a timer. eg. if RAND <= (some ultra-low percentage chance)(a modifier(s) perhaps) then apply bonus. Checks on a set interval.
I just don't think it is an event trigger because eventually what it was would get out and that's all people would do. From what I can gleem about chadz he does not like that sort of thing and would have planned against it.
I remember he said he wanted to implement something where you got better at your weapon/armor the more you used it a long time ago so he has plenty of time to think about how it would work.
I personally think it does no stat change. It just a reminder, a little pat on the back so to speak, that lets you know that 'THOU' have gotten better at using that equipment, not that the avatar got any bonuses. Or at least like to think so.