All right, I don't see it here, so I'll mention it.
I've noticed what seems to be a bug with allied lords and merc companies, perhaps even allied non-lords who join your battles. If I join an allied lord/merc company who is engaged in combat, I get a portion of the knocked out enemies as prisoners and can recruit a portion of the enemy's former prisoners, and the allies who fought get whatever I don't/can't take.
However, if I start a fight and have those same lords/merc groups join me, none of the allied armies can recruit prisoners or take captives, and anything I can't hold is just lost forever.
Is this intentional? It really sucks when I marshall a few armies to fight a bloated unique spawn or 1200+ man super invasion army, lose a bunch of soldiers from all allied armies, and then am the only one allowed to replenish my troops afterwards.
On another note, I've heard that the merc companies should no longer run from enemies when accompanying the player, but this is not true. Every company I've hired has run from any unique spawn I've seen, and run so far away I can't even drag them into the fight anyway.