well moirails are a little different than just "best friends"
like, you also have to a counterbalance to your partner's personality, and you're in many ways a life mate with an even deeper relationship in a few respects than a more romantically inclined one
so saying that gamzee "was" his best friend could just be representative of the shift in their relationship from friends to moirails
that's more words than ever wanted to write about troll romance
--
bad advice
http://www.last.fm/user/snowcampsoldier