Actually there's a rule that eveyone should follow.
Thou shall not merit a post that doesn't meritorious.
Thou shall not buy merit it will be tag in your DT
Thou shall not exchange merit for a certain amount of fiat
Thou shall not sell merit it will be tag in your account

That being said merit sources need to look closer to a post than normal user.
I hope I make it clear stating the normal rules we should obey according to forum history.