As has been pointed out a few times already, the real reason it shouldn't be done is because the post author is taking credit for something they didn't write, wanting everyone else to believe they actually did write it. This is one of the most direct statements on AI policy that we've had from forum staff thus far:
It should be treated the same as plagiarism. Asking an AI something then copy and pasting the response is just as bad if not worse than plagiarism because it's not as easy to detect, though the posts do kind of stand out.
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I think theymos should probably make an announcement about prohibiting this sort of use of AI or at the very least we add it to the "unofficial" forum rules but users should be alerted not to use it in such a way. If a user if just going to use it to copy and paste the title of a thread or the OP into an AI then copy and paste the results that should be treated the same as plagiarism. If it isn't then this place isn't going to be a discussion forum for much longer but just a get paid to copy and post AI responses forum.
If you insist on posting text written by ChatGPT, it should be done as an attributed quote, like such:
Here's what ChatGPT had to say about this issue:
To avoid issues related to plagiarism, it's essential to provide appropriate attribution when using information obtained from ChatGPT, especially in contexts where academic, professional, or ethical standards apply. This involves acknowledging that the content is generated by a language model and providing references to the model and its training data when necessary.