Okay, seeing as occasionally people complain about their threads getting locked and they don't know why, I've come up with a simple idea on how to solve it:
How about Mods can fill out a little form that goes on every page of the locked thread, explaining why is was locked? That way, people can't complain about their threads being locked for no reason. It can go oon the top and people will quickly see it.
Yes, for the record I try to write reasons for every thread I lock.
...and yes I also have a range of locking pictures. But they're a bit cryptic.
Personally I'm not sure that the form would change our behaviour in this regard. I always take pains to explain as a personal preference because unless it's old and dead and really has no place on the front page, at least it can serve as an example of what kind of things not to do in these forums.