Believe me, I'm completely with you on this. It is perpetuating the Zeppo myth. But in The Zeppo, I couldn't buy Xander's insecurity OR the Scoobs' low opinion of him. In The Replacement, I still wonder when Buffy and Willow started thinking so poorly of him, but I can at least buy Xander's insecurity.

Overall, though, you're right. It's like the writers completely forgot about the character they created and replaced him with the doofy "comic relief" except that he IS the joke instead of making the jokes. Calling him the "heart" is just pandering and an excuse not to give him a real arc.