It is a bit crazy to me someone posts a regex like that without verifying and saying on surface level it looks good, implying the whole thing was useful and a good result.
I said it looks ok, not good. My comment is mostly about me being surprised a valid regex came out. I also asked it to write a regex to parse html which it happily answered. What does gpt4 say about parsing html ;)
But it is either going to be useful or harmful. Harmful if doing the regex validation itself is worse than not doing any validation at all or a very simple validation just checking that there is @ included somewhere.