I think merit points should only stay if the post was deleted by a moderator, or the owner of a self moderated topic. If the post is deleted by the user, the sMerits should return to the person who gave the merits. If merit selling/trading was to get popular, it would be fairly easy to hide who you bought the merit from or traded with, as you could make a temp post, wait for them to "pay" the merit, and then delete it, hiding all traces of the "trade" from the general public. Thoughts?
I don't think it works like that.
The merit point will still show on your profile along with the username that gave it to you, just the link with the reference will point to an invalid post.
Lutpin was about to to test this...
The merit page should indeed be public like the trust page:
https://bitcointalk.org/index.php?action=merit;u=xxxxxx