I'd recommend IP banning after having banned someone by their Steam ID after they have rejoined under a different steam account. Once they do that, ban their IP, and if they aren't smart enough to figure how to get around that, Good Game! But make sure to simultaneously ban their 2nd account's Steam ID as well!
There should be a way to see their name with their pic beside it when ur trying to kick through menu XD since ur seeing their name... it should put a picture beside I so u know which is which! lol