So I think this merit mechanism is unfair, because it would allow those legendary or heroic users to profit from the merit mechanisms, and not to upgrade those who can not afford it.
I'm definitely coming from the opposite perspective here, as being here on these forums for a while and finally reaching a high ranking. However, I don't think this system is particularly unfair. Those who have merit will not be selling it; hero and legendary members at this point in time know better than to sell their merit. Even if it is being sold, it ends up being pretty obvious because all you need to do is look at the suspects posts and who merited them.
There's nothing about affording here; merit is not a form of money. It's (I guess) just another way of protecting the forum from spammers who are just trying to get into sig campaigns.
I agree. I don't think hero and legendary members will sell their merits, they aren't that stupid. They have earned everything in a very fair and just way, doing this will ruin their reputation. Also, these high ranking members (I think) doesn't need to sell their merits since they have enough money coming from the forum and other forms of bounties. Selling merits is just a petty thing to do.