Furthermore it's probably in YC and their founder's interest that people not know what they are working on until they feel ready to disclose it.
Thats why we built it!
It would be better to use flash for demos.
And perhaps more angels/VCs would check out your startup as well.
An adjustment to your idea that I'd feel more comfortable about would be having an url field next to your name in comments/submissions. So your comment would look like: 1 point by amichail (mystartup) 3 minutes ago
For example:
username, prototype link, brief prototype description