Yes I know there are several posts in various places about people writing this mainly on social media and not understanding why but the argument 'for' it is that it sounds like could of, would of etc so people write what they hear. Which I can sort of buy but will never agree it's ok.
But the other day someone actually SAID it to me. I've never heard anything before other than could've or could have actually spoken. This was a mid 30s guy who is a civil engineer so has a university education and is a member of ICE.
Now this I found far weirder than someone writing it.