You can get this answer for any user by looking at their profile - there is a 'favorite' link at the bottom, and then a 'comments' link at the top of the favorites page.

And if you don't have specific user you want to look at, you can look at the top 100 users here: https://news.ycombinator.com/leaders

You can also find the recent "best comments" here: https://news.ycombinator.com/bestcomments