The web doesn't need another poorly implemented API

Under minor trolling accusations (https://github.com/w3c/editing/issues/88),
I reiterate here:

There is no need for such an API. I feel that the contentEditable stuff
should just be deprecated.

For two reasons:
1. There is no way that browsers will implement such a complex API in a
reasonably consistent manner.
1. It is possible to write client code that implements all of this, without
using any contentEditable at all.

After dealing with current `designMode` and `contentEditable`
implementations, I can tell you, they are bad. But you know that. What
guarantees that implementations of this will be any different?