The incentive to respond is the content of the email (or the identify of the sender). If I want to "offer" the receiver of the email an added incentive to respond I can say so in the email. "Respond to this email and I will give you $1000."

Interesting idea, I think you need two things though:

1) Better copy. I (and others here I'd imagine) have no idea what exactly your site is. A short blurb that's a couple of sentences long that explains what is helps greatly.

2) Post this as its own post instead of a comment in another post. This way it looks a little spammy (which I understand is not your intention). Make sure you mention how it's built in Arc in your title, and post a story on http://arclanguage.org as well (if you haven't already). Beware that new accounts posting links often get marked as spam, that's why pg recommends you have an account for a few weeks before doing a Show HN post, which would be the type of post you'd do in your case.

Good luck!