I am not sure if I understand your first question, but the second one is a genuine and known concern. I assume selling merit will result in negative trust feedback, but it will probably not result in users losing their rank.
If you are asking on how did the merit system affect higher rank users, well, it depends.
Legendary members are obviously not affected by this in a negative way at all, since they can't rank up anyway.
As for Hero and Senior members, they got some merit in the begging, but it made it very very hard for them to rank up further.
Closer you were to ranking up, more negatively did the merit system impact you.
If you were a week or two away from ranking up, like I was, then a sudden requirement of needing 150 merits slowed down your ranking up a lot.
I was lucky to get the merits I did, but I still haven't ranked up since the merit system was introduced.
Merit selling can only result in a very limited harm. I have discussed this before:
a) You can possibly sell you initial merit. This is just a little amount and once it is gone you can only get it from a merit source. Thus, the damage is limited.
b) The remaining option is to buy from a merit source. This could only be done in limited manner, as the merit given by sources is public and, eventually, forum members would discover it (post of low quality merited, too much merit to the same users, etc.)
So, the system is not perfect, but is not that bad.