Some people are informally "banned" from working on whole categories of open source projects because they've had provable exposure to closed source code in the same domain.

That's a partial motivator in maintaining pseudonymity online. If no one knows who you are, and they don't know you've done kernel work at Microsoft, you or the open source kernel project you're contributing to can't be sued by Microsoft, hypothetically, for "inspiration".

There's legal questions here for which there's never been precedent, so nobody knows where the line is -- and this is all before LLMs ever entered the picture. For other countries, whose courts don't rely on precedent, it's even more of a minefield since the legal outcome of a case is always undefined behavior.