Really? What do you think this link is? It just goes to a landing page to sell you and get you to sign up. This is an obvious advertisement, why do you only notice when someone makes it a comment instead of a link?
However, when you use marketing babble in a comment, it adds no value to the conversation. "Join millions of..." that is just not helpful to the HN conversation.
Now, if the comment was -- "we developed this to try and solve X problem for Y users. Let use know what you think or if you have questions..." -- then it might have been a useful place to start the conversation. Marketing copy is not.
(And they probably did more harm than good by posting that comment)
Submitting a startup is very much permitted on HN. [0] Startups are the business Y Combinator are in, after all.
I assumed, as you did, that amig0ld works for this project, and is cynically ad-spamming HackerNews. My comment was intended to invite a meaningful reply. This now seems unlikely, but it was worth a shot.
(The amig0ld account was created January 2013. Its only other activity was in May 2013 - another self-promoting submission.)
Are you associated with this project?