I'm going to guess the poster was banned for something a while back. When you're banned on HN, you aren't locked out of posting, but everything you post appears as dead by default and requires someone to vouch it.

dang has talked about this before, but there are a number of users who were rightfully banned, go on to post nothing but healthy, constructive comments that almost always get vouched, and then immediately turn abusive again when they're unbanned. So the current moderation philosophy is to leave them banned and let users vouch their comments, which works out better for everyone.

Something automatic due to post history maybe?