Posting in a megathread is pointless, but then so is posting in any other thread on this forum. Have you seen how many pages of threads there are just in this subforum?

By discouraging megathreads and encouraging new threads you just shift the problem.

That problem is that there's way too much noise on too little valuable content. The merit system is one attempt to curb the amount of low value content, but so far it still doesn't seem to be very succesful.