"...it's frighteningly easy to plant false memories in people's heads ..."

And that's why it is very difficult to ascertain whether a 'memory' is of an actual experience, or assembled pictures and ideas from things they have heard about or dreamed about. We DO know of many verifiable instances of the latter, and can even work out much of the mechanism whereby it works, but how a memory can BE passed from one life to another is such a puzzle that buying into the idea is fraught with traps...