Counting Comments Per User

So… If I require registration on my site, then if I click on “users” and go through the list I should be able to see which users have left comments and which have not.

However, the list of users has a number under “posts” and I can’t tell if it’s only referring to actual posts or if comments are supposed to show up too. If the former, where can I get a list of which users have commented and where? Is this only possible with a database query?

Thanks!