I don't think I've ever seen a thread on Cassiopeia or the lore retcon in which the majority of posters (and often the OP) weren't being huge dicks/overwhelmingly negative. I imagine that has something to do with it.
This format as a whole doesn't really seem to encourage 'highly debatable posts.' It's good for sharing your personal creations or arguing about menial shit like itemization, but that's about the extent of it. What happens with Cassiopeia threads in particular is that people spam upvote it, and anyone who disagrees that Cassiopeia was a mistake gets spam downvoted until they're basically a nonpresence in the thread. Individual arguments might happen, but the thread itself is basically just a platform for the OP and their friend's position. Making it the post of the day wouldn't actually be drawing attention to this hot, back and forth debate - it'd be drawing attention to the 50 or so people out there that share a certain opinion.
I'm pretty happy that whomever runs the post of the day represents the community at its finest. Character concepts, theories about lore, inoffensive suggestions - these are all things that the community can actually produce and handle at a high quality level with reasonable civility. It'd be odd to me if a 'debate' thread was actually high quality enough to warrant being put on a pedestal, given that debate threads in general are pretty shit on these boards.
