Using Font Awesome for the icons to social services works great for commercial services, since most if not all of the prominent ones have their icons there. However, those of us using free / open source social services are (I think) less lucky.
Any suggestions about how to add icons for e.g. Riot.im / Matrix, Mastodon, GNUSocial, Diaspora, IRC…?
Exactly what identity are you trying to prove here…? NickServ registrations expire after ~90 days. The email usually isn’t verified or even available to other users.
You can prove identity over IRC, and I’ve done it before, but I see absolutely no reason for Discourse to implement or support that. (And even then, it was with considerably stronger identity guarantees - Twitch IRC.)