Hacker News marketing skills tell people to leave a context comment on Hacker News. Don't complain about it too much, that is our way of figuring out who is lazy in an obvious way!
When someone makes a submission, the text field becomes a comment when the URL field is not empty. (but sometimes not?) It's a poorly designed form that should be redone.
Presumably if the protocol becomes popular you will have public instances that anyone* can sign up to, the same way other federated services work now.
(It's approximately as hard for a layman user to sign up to a Mastodon instance as it is to sign up for X. The fact that most layman users don't do that is a separate issue.)