As of May 8, 2019, GitHub added gist notifications natively. We're disabling the service, but keeping the site up for posterity.

Giscus provides the comment notification system your Gists deserve.

You love Gists. They're powerful, free, and convenient. But you've probably run into Gists' one big downfall: No notifications when anyone comments.

Receive up-to-the-hour notifications on comments on your Gists. No work on your part, free because Tighten loves you, cancel any time.