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.
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."
Sometimes, the incentive cannot be monetary, because the recipient is not interested in money. What the recipient may be interested in is an indication whether it is worth investing in a reply.
We had changed "pays" to "helps" at an earlier stage.
We are not spammers. This is in Arc, but written from scratch.