People I've worked with have different philosophies on this, but personally, if you check in code that is distinctive enough that I can identify the source you copied and pasted it from, and you provided no indication (whether in a comment or a PR description) that you copied it, I will really get quite grumpy at you about it.
Way too often I burn half an hour needlessly during review in one of two ways:
* trying to figure out how the heck someone figured out some "magic" code that achieves something by invoking a bunch of poorly documented library or framework internals, and trying to reverse engineer WTF all the magic does by diving into the framework's source... only to eventually think to google the whole snippet rather than each individual method call, and discover it's copied from a Stack Overflow answer
* trying to figure out why something was written in an unidiomatic or overcomplicated way rather than a more obvious approach, and commenting at length on how I'd simplify it... only to eventually realise it was copied from a Stack Overflow answer
Attribution isn't just about making sure the right person gets credit, or about license compliance; reviewers and maintainers frequently need to be able to see where stuff was copied and pasted from in order to do their jobs effectively, even for snippets of just a few lines.
I understand where you are coming from. However, I think you are making the assumption that this person simply copy/pasted some code with no understanding of it, or that this code is then very different from your codebase and needs to be refactored. If using Stack Overflow did not add to your overall development time but subtracted from it, because it was used as an appropriate piece of a much bigger puzzle - a far more realistic scenario for both Copilot and our general use of SO -, then I see no issue with it whatsoever. Certainly no moral or copyright issues as this person on Twitter implies.
No copyright issues in the sense that no entity is likely to ever pursue the matter, sure. But copying and commercially using someone else's nontrivial bit of code that doesn't have a license that says you can is quite blatantly a copyright violation.
Way too often I burn half an hour needlessly during review in one of two ways:
* trying to figure out how the heck someone figured out some "magic" code that achieves something by invoking a bunch of poorly documented library or framework internals, and trying to reverse engineer WTF all the magic does by diving into the framework's source... only to eventually think to google the whole snippet rather than each individual method call, and discover it's copied from a Stack Overflow answer
* trying to figure out why something was written in an unidiomatic or overcomplicated way rather than a more obvious approach, and commenting at length on how I'd simplify it... only to eventually realise it was copied from a Stack Overflow answer
Attribution isn't just about making sure the right person gets credit, or about license compliance; reviewers and maintainers frequently need to be able to see where stuff was copied and pasted from in order to do their jobs effectively, even for snippets of just a few lines.