My biggest problem with this is that if a post that doesn't belong gets upvoted it'll reach the front page, and once it reaches the front page all of the worst

My biggest problem with this is that if a post that doesn't belong gets upvoted it'll reach the front page, and once it reaches the front page all of the worst parts of Reddit flood into the comment threads. /r/coding has stricter moderation, but much much less content is posted there. People generally want to post their links where they'll garner the most karma, and cross-posting feels kinda dirty.