Note how you almost never see spam on GitHub. And you can effortlessly cross-reference issues across repos and notify other users by mentioning them. That works, because global view across all repos makes spotting and blocking abuse easier, and moderation is possible thanks to the business side subsidizing it.
Contrast that with WordPress trackbacks. They're all spam. And blog comments are full of spam too, because individual operators don't have know-how to fight them, other than outsourcing spam filtering to… a centralized service.
Note how you almost never see spam on GitHub. And you can effortlessly cross-reference issues across repos and notify other users by mentioning them. That works, because global view across all repos makes spotting and blocking abuse easier, and moderation is possible thanks to the business side subsidizing it.
Contrast that with WordPress trackbacks. They're all spam. And blog comments are full of spam too, because individual operators don't have know-how to fight them, other than outsourcing spam filtering to… a centralized service.