on my windows chrome (Version 80.0.3987.149), the "bug" is clearly there. see attached. that you don't see the problem looking at the html doesn't mean it isn't there.
the return/enter key generates a new node. when you hit the backspace key, the new node is not un-noded back to original version. bug, feature, or failure in re-inventing the wheel - it is what it is. (which, by the way, is not a bug attributable to webview)