Most of the debate here is that a lot of us don't find YAML anchors attractive. It can be one of the papercuts of using YAML.

I mostly agree with the article that with GitHub Actions specifically, I try to refactor things to the top-level "workflow" level first, and then yeah resort to copy and paste in most other cases.

I'm a little less adamant that GitHub should remove anchor support again than the original poster, but I do sympathize greatly, having had to debug some CircleCI YAML and Helm charts making heavy use of YAML anchors. CircleCI's YAML is so bad I have explored options to build it with a build process. Yeah, it does create new problems and none of those explorations got far enough to really improve the process, but one of the pushes to explore them was certainly that YAML anchors are a mess to debug, especially when you've got some other tool concatenating YAML files together and can result in anchor conflicts (and also other parts of the same YAML that depend on a particular form of how anchor conflicts overwrite each other, oof). I don't see GitHub Actions necessarily getting that bad just by enabling anchors, but I have seen enough of where anchors become a crutch and a problem.