I use the report " Match items on your Wantlist with items on other members' For Sale / Trade" all the time (football). I have 77 sets listed and only a few of them has more then one card. No way to sort out players so I have to do it by the sets no problem for me. (only 77 of them) Like udelljaru There is a lot of clicking to find stuff. Out of the 77 matches half of the members are NOT active now. I have to check all sets just in case they come back.
I contacted Adim about having members that have not logged in for over a year (or so) that their lists would be hiden. I would say 6 months. He though it was enough that I could find out by looking when they lasted logged in. Yes that works so I do not make an offer but waste time.
I have been asking COMC to do something about hiding all the cards I have when pulling up a player for over 5 years. They see no reason to do it. I waste a lot of time looking through cards I have before I get to ones I need. (willing to buy)