I've seen that hair extension removers have the same ingredients and smell exactly like nail polish removers. They dissolve the keratin glue. Do they affect human hair in a bad way..? Weaken it? Or is it safe to use?

I dont think they would use a remover bad for your hair cos you can sue if that happens

Doesn't sound like a good idea to me. Use what is meant to be used to remove hair extentions and nothing else.