Steps to reproduce
Go to a work or news post
Scroll to the comment form
There's nothing telling you you can use HTML in your comment.
What should happen
At the end of the statement "All fields are required. Your email address will not be published." there should be another sentence: "Plain text with limited HTML" which should have a help link to https://test.archiveofourown.org/help/html-help.html at the end, like it does on the logged in form.