Find any work or admin post that allows guest comments
Enter a comment, but leave out one of the required fields (name or email)
Attempt to submit the comment
Note the comment is not accepted, and the form validation points out the missing field (as expected)
Note that the "Comment" button is now displayed as "Please wait..." and has not reverted
Note that the comment form can no longer be submitted, the button doesn't do anything. (Refreshing the page will fix this, but you might lose your comment)
I’m going to close this – we’re using as a catch-all for these issues, since the fix will have to apply to all cases.