You think that you are adding a description for your post when in fact you're simply submitting a regular comment not promoted or distinguished in any way.

It's even worse considering posts without URLs would take the same text from the same input box on the HN submission form and append it under the post title, locking it to the top of the page - so if you've browsed linkless posts you think maybe the submission text is gonna end up just like that, but it doesn't. (Also I think you'll even see URLs like an archive link end up appended just below the submission title for URL posts. Which I guess is a special feature.[1])

Any reason I should not send HN an email requesting clarification of this the submission page?

Edit: quoting https://news.ycombinator.com/submit :

  “If there is no url, text will appear at the top of the thread.”

[1]modpowers(?) used to directly append links to URL submissions further confuse the matter: https://news.ycombinator.com/item?id=49243880