There seems to be something misconfigured in Github–if I click on a pull request, then try to click on a commit directly from the “Conversation” tab, I get a 404 error, as the link is pointing to https://github.com/<commiter's ID>/vassal/pull/..., whereas if I go to the “Commits” tab, the links work, and are pointing to https://github.com/vassalengine/vassal/pull/....
This was working fine a day or two ago.