I thought people were saying that Microsoft removed the copyright headers and replaced them with them, which they did not.

Microsoft replaced the LICENSE for the whole repository with their own, and thanked Spegel in their README. While this is some kind of attribution, it's not enough for the MIT LICENSE. I don't know exactly what would be good enough, I think having a copy of the Spegel LICENSE file somewhere in their repo would be enough (though possibly less visible than the line in the README, to be fair).

My overall point is that it feels like people are complaining a lot about what seems to be an honest mistake. And not just that: the way Peerd did it is arguably giving more visibility to Spegel than if they had just copied the licence somewhere in their repo. Peerd could possible just copy the licence somewhere less visible and remove the link from their README.