It can be both quite often true and quite often false. Thank you especially for "source amnesia", it's perhaps the most important part of the phenomenom, though doesn't fully explain it.

My experience arguing with other people is that you cannot change a person's deeply held beliefs

My experience is it depends on the person, and how much their environment reinforces those beliefs.

If you want any chance of success changing someone's mind, correct them on easily verifiable facts, not on complex topics.

While this is good advice, I think people incorporate much more from an argument than they explicitly accept or recall. It takes time for good arguments to sink in, and that can happen even if you don't consciously think about them.