Disqus is quite widely used, so yeah there's the benefit of a lot of people already having an account.
Probably the only thing I can think of that would be even wider would be Facebook, lots of site have Facebook comments sections where people can comment with their Facebook accounts. If someone's logged into Facebook in their browser it'll even show up with their name and stuff ("Hey polak, comment on this article:").
https://developers.facebook.com/docs/plugins/comments/
EDIT: This is one I've always wanted to give a try as well, seems well done but I've never used it and have only seen it on sites a few times.
https://muut.com/