1. We use aged Github accounts, SMS verification, BrightID, a few other undisclosed vectors, and (soon) Idena Network/ other DID solutions, as an identity solution for Gitcoin Grant contributions. Check out the trust tab of your profile to increase your trust level.
2. In addition to Github's native anti-sybil technology, we programmatically check these accounts for signs of Sybil attacks. Each contribution is assigned a trust score according to the likelihood that it's part of a Sybil attack. Right now we do not take any action against Sybil attacks (other than the most egregious cases), but we are quietly collecting data to use in the future.
3. We use Vitalik Buterin's pairwise bonding formula to dampen Sybil attacks => https://ethresear.ch/t/pairwise-coordination-subsidies-a-new-quadratic-funding-design/5553
More on our anti-sybil growth strategy here https://twitter.com/owocki/status/1273458452900151296