But I think varying amounts of the HN audience are unfamiliar with any given topic that might seem like old news.
Not all submissions are driven by marketing sockpuppets.
I get that there's always one of today's lucky 10,000, but I think a certain threshold of obscureness is reasonable. It wouldn't make sense to submit the Linux Kernel project, or Mozilla Firefox without any news.
Maybe I'm overestimating how well-known ReactOS is, though.
Though now that you mention it, it would at least be a little bit funny to submit kernel.org and be like "Found this cool indy OS kernel, looks like it's just a hobby and won't be big and professional like GNU but it's still neat" in the comments :)
Do you believe that most of the HN audience know ReactOS very well? I upvoted the submission, because I don't think so.