I do think it's a big case of appearances are deceiving. AS well as the reasons you list, the biggest one is probably just that Mutant Enemy were nervous about showing a lesbian relationship on screen in season 4 and only hinted at it obliquely - such as Buffy being surprised to come home and find Willow's bed hasn't been slept in, but doesn't ask her where she was, and the notorious use of 'casting spells together' as a thinly veiled metaphor.

An interesting follow-up to your survey, incidentally, might be to ask the demographics of the people who hate each character. I can certainly imagine reactions to Kennedy being split between straight women (she's far too pushy! What a bitch!) and straight men ("Wow, I wish attractive women would come on to me that blatantly!") with lesbians perhaps being divided between those two opinions...