I loved Reddit for what it is, but nothing made me back out of a post faster than seeing the top 3 parent threads as a regurgitation of the same inside jokes, pun-chains, and so on.
@bizzwell some subreddits did have some dedicated flairs which required everyone to be serious (at the cost of being banned) - but this required the OP to deliberately think about posting the stuff under the right flair.
Maybe this could be also easily enforced here by asking people to append [Serious Discussion]
at the beginning of each relevant post, on the title or content?