It also depends on the level of antisocial behavior for the character. It doesn't always have so much to do with the mun. For example? NO problem getting Buffy all diversified. Katniss, however? Hahaha, ha. HA. It takes a seriously attention-gripping post for her to talk to people who aren't her castmates. It's... just how she is. For some characters it would be pushing boundaries of being IC to force people to tag different characters every single month. Cross-canon isn't an issue so much as a constant requirement to tag someone completely new when it would be flat out OOC for some characters to do that without a very, very good reason.