I miss in this whole thread why this is happening. Presumably to be transparent whether code has been co-written by AI?

What's in it for Microsoft?

If we accept that AI can't copyright or own IP rights on something, then why? I have a sneaky suspicion that there's some lobbying in the works to overturn that ruling going forward. In the past, it was OK to build models from copyrighted data etc one might have found on the wayside. But, in the future, no such thing for you. Everything generated by the AIs will then belong (at least partly) to the megacorps (maybe THEY can co-own the copyright if the AI cannot). Nice pulling-up-the ladder if true.

This could also be a move against other countries' IP position.

I've seen the explanation from dimitriv [1], but I am not convinced. These markings achieve very little, as people can clearly work around it by copy-pasting code from another place, or using other companies tools, like claude code or antigravity (or, not even use the GUI)

I suppose the answer might just be "don't attribute to malice ...", even if Microsoft has proven us wrong before; they generally know exactly what they are doing strategically.

I guess, in a few years we will know.

[1] https://news.ycombinator.com/threads?id=dmitriv#47991835