The way I see it, if you would use Copilot to completely (or largely) reproduce an existing work (software), then you would be infringing copyright. This is similar to using an AI to largely replicate a piece of music.
If you are using it to mix a snippet of code (from a sufficiently large code base) into a large code base of your own, then you are just remixing. That is not infringement. In music, there are entire genres based on remixing. You could even take it a step further and ask yourself: what is not a remix?
Yeah, I've heard about some of those cases. It's surprising how far copyright can be stretched sometimes.
What's more surprising is to see copyleft advocates positioned so strongly in favour of giving copyright that kind of reach. I think that in a different context, some of the cases you refer to would be used by these same copyleft supporters as examples of why copyright needs to be more weakly enforced, not more strongly.
At the very least it should be consistent. If Microsoft can sue me for something trivial that probably shouldn't be illegal but is, then I can sue them for something trivial that probably shouldn't be illegal but is.
If you are using it to mix a snippet of code (from a sufficiently large code base) into a large code base of your own, then you are just remixing. That is not infringement. In music, there are entire genres based on remixing. You could even take it a step further and ask yourself: what is not a remix?