Err, the Gamzee/John kiss probably didn't happen, it is drawn in the style that Hussie usually draws things that aren't really happening.
Well then there are two ways to take it that keep the fact true.
1) It happened in the comic, but not necisserally in the reality of the comic.
2) There’s still Gamzee’s implied sloppy makeouts with Tavros’ head.
Take your pick.
-Mod L