The way I see it, post quality could never be determined by some sort of comment-length count, bot, or anything that doesn't involve the community. The reason the upvote / downvote buttons exist is to use the people of the site to determine post-quality.
I'm also new here, so I feel pretty lame posting my opinion, and my idea of this site is probably completely opposite of what the veterans use the site for, but I started lurking on the 3rd and I really haven't seen any low-quality posts. Maybe the discussion can wait until things start actually going downhill? It seems drastic to change the way the site works just because a bunch of us are coming from Reddit. I can't blame anybody for being concerned, but I think that most of us that are coming from Reddit were probably Reddit users for 4-6 years.
I don't know what the post-quality looked like before the 3rd, so maybe it's already going downhill, but I honestly haven't seen any problems.