The "humans do it, too" or "humans have always done it" arguments break down very quickly.

Not only by comparing the scale of infringement, but because direct Stackoverflow snippets are very rare. For example, C++ snippets are 95% code cleverness monstrosities and you can only learn a principle but not use the code directly.

I'd say that Stackoverflow snippets in well maintained open source projects are practically zero. I've never seen any PR that is accepted that would even trigger that suspicion.

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