zlacker

Looks like it's one of these:

  .alt-mono-font {
      font-family: SFMono-Regular,Consolas,Liberation Mono,Menlo,Courier,monospace;
  }

If you find yourself wondering this a lot, https://chrome.google.com/webstore/detail/whatfont/jabopobgc... is a fun extnesion.

>>alecbe+(OP)
If anyone from GitHub's around in this thread, would you mind putting "ui-monospace" at the front of that list? SFMono-Regular no longer works in Safari because of fingerprinting concerns.