Are there any plans to include “friend” features such as communication between friends and viewing other users’ game libraries? Perhaps some matchmaking features for players, I think Strider might have mentioned this in a video somewhere?
“Lutris Liasons” perhaps 
Sorry, I looked in the forum for this but didn’t realise it was already mentioned in the “about” section of the main site!
Yes, this is planned indeed!
The matchmaking feature will be called Offline multiplayer lobby. It will allow to do the matchmaking while players are not running the game, which is useful for games that don’t have a lot of players.