I believe what that URL should be is a matter of opinion.
The POST hook is trying to provide information to an automated system. If that system wants to do more I could see it wanting both the API link and the website link.
For now we are going to leave the link as the API link.
Except the link with the API sub domain is 404ing. How is that correct, in any way?
The API sub domain link 404s.
Yes, @Dylan Etkin should not have closed this. That URL is plainly invalid.
The html link should now properly point to the pull request, and all API links should be working properly as well.