Say I was Posting spam questions and answers in the Battle Subway, but not Pokebase, could I get banned in just the battle subway?
Nope. Mods can choose to block the account's IP or their entire account, and both of them are global bans that block you from everywhere. We can't choose where we block them, and we shouldn't need to since any user who is toxic in one section is probably the same in any other one as well.