Post an inline comment when not logged in is very weird.
You can get in an endless loop between the login page and the discussion, while the comments continue to post.
We should a) fix that loop (threadedcomments is redirecting to the previous page instead of the correct URL),
and b) make the inline message just tell you to log in, eliminating the entry point for this bug.
SixLinks Developers' response:
This is a big one, and we'll get it fixed!