There's a marketplace forums? Oh you mean that attempt under D7 forums? Noone uses it, so regardless of the intent, it's not a good venue to make these comments. Plus, it would just turn into a spam forum if it was frequented and the kudos would be way at the bottom.

The best way I see is to comment directly on a modders profile and then have the newbies check those comments. Harder to get rid of profile comments. Actually, I haven't found a way yet.