But it doesn't here! You are totally allowed to completely copy an MIT file, modify it and add your copyright to it!

You should just keep the copyright that is already present in the file! But in the case of Spegel, I don't think that the files contain a copyright header in the first place.

Nonsense. Copyright is implicit and assigned on creation.

The git history has a clear trail showing author and contributor details.

An explicit copyright notice for every file isn't needed.

This is a straightforward, unquestionable license violation, and no amount of corporate FUD will change that.

You're talking about copyright, I'm talking about attribution.

Of course, the author keeps their copyright on the lines of code. But that's completely different from how the attribution should be done.