Insta-logout does not work because of aggressor flag. Aggressor flag should be cleared immediately when you kill monster (not player). You have to wait two minutes, if you attack monster, be it self-defence of intent, no damage is needed.
Camping does not work because of skill timer. You cannot logout when you are in period when you can't use another skill, like 10 seconds after you hide. Camping haven't had skill timer long ago, but I think that it does have (small) one right now. Well, may be it is action timer not skill timer, I don't know exactly, it is only educated guess. Camping skill itselfs succeed, so you are allowed to logout, and client disconects, but logout functions checks if you are in skill timer and because you are your avatar stay logged in. As programmer I can see reason here. Server need keep your avatar in game until given action is completed as there are skill which kick in only after timer. On the other side, such stupid problems suggests incompetentness in UO team.
In both cases you are logged out after five minuted of inactivity.
In both cased I think that timers should stay, but mentioned problems should be resolved.