Hm, there (sorta) are two positive feedback things in place. The first being a friedlist and the second being the clan. However they are both quite lacking.
There is a somewhat hidden 3rd thing as well. When you create a game, in the invite players tab: your friends are sorted by number of common games. Not sure I would want a public 'reputation' system. But this uservoice is quite popular : https://warlight.uservoice.com/forums/77051-warzone-features/suggestions/1142113-add-a-friends-list-subset-to-the-invite-list