After an interesting and informative round in my questions about how whips work, we stumbled upon yet another conundrum that I hope to get a solid answer for.
The main question that came out of it was:
Can an Attack of Opportunity (AoO) cause another AoO?
Creature tries to run away from me (el oh el), as my AoO, I replace my melee attack with an attempt to trip the creature. This attempt, according to Trip, triggers an AoO against myself. Does it?
What is the limit on this if Combat Reflexes is involved?
Can something you are fighting actually provoke an AoO on your turn without feats? (The argument to this was no, because feats like Greater Trip pretty much rely on the fact that you force an AoO rather than it not happen)
Yes, you can get chain AoOs happening, theoretically all the way up to the limit of Combat Reflexes.
As for an enemy provoking an AoO on your turn, I think the only way it could happen is if you have provoked an AoO from them, first, though there are situations where a readied action could cause it. Sort of.
1) An AoO can cause another AoO.
2) If you attempt to trip an enemy on an AoO and don't have Improved Trip, yes, they'd get to hit you back. If you had combat reflexes, and they tried to trip you on their AoO, you would in fact get another AoO against them.
3) The limit on this is the number of AoOs you can make. For Combat Reflexes, that's 1 + Dex mod
4) An enemy you are fighting can provoke an AoO without feats--if you attempt to use a featless combat manuever on them, and they attempt to use one in return as their AoO, they would provoke.