Currently just Show HN. We don't do it for other kinds of posts for reasons explained in the FAQ (https://news.ycombinator.com/newsfaq.html):

Q: How do I make a link in a text submission?

A: You can't. This is to prevent people from submitting a link with their comments in a privileged position at the top of the page. If you want to submit a link with comments, just submit it, then add a regular comment.

The difference with Show HNs is that when it's the project creator sharing their own work, it's ok for their link and text to be in a privileged position. Hopefully people won't start abusing that, but if they do, we can roll back the change.