The help center page on privileges says "flag posts", but that privilege also includes the privilege to flag comments. I propose changing the text to say "flag posts and comments".
It would follow to also change the heading in the "flag posts" privilege page to say "flag posts and comments" instead.
I'm guessing those changes should be easy. The awkward what-follows-next is: change the page URL from "flag-posts" to "flag-posts-and-comments", which I don't personally care much about whether or not such a change gets made. But if it does, then it would be nice for the old URL to redirect to the new one so the old links don't rot. I say "awkward" because I'll bet this is not a quick and easy change to make, and I'd rather not ask for it if it would prevent the other probably-easy changes from being made more quickly.