I'm okay with a collab post myself so long as it's not too padded out, the players are in character, and it doesn't exclude people from interacting with a GM post by having too much time go by. And also once in a while since other people would feel left out if it's constant and I think it's easier on the flow of narrative if people didn't constantly have to bounce around perspectives in a single post. Generally I'd prefer it if the scenes were isolated to the two characters in question if it's going on since it'd be awkward to get in on it with anyone else around. My sub-GMs can tell their own opinions on this if I've missed anything. 

Also um, yeah. Omniscience is a thing that I'm not okay with. If you want to interact with someone, then just having focusing on one area is better than knowing everything going on at once. Also once again saying that if you haven't put a really significantly powerful skill/ability/item in the character sheet and you use it in the game, that's grounds for me to take out the nerf bat.