Re: enriched-mode and switching major modes.

[Richard Stallman]

    1 - it does not preserve the identity: the text-propeties belong to
        characters, not to some external object.

I already explained why I made that change.

    I think the semantics of `duplicable' extents is clear when the ducplicated
    text includes the whole extent, the problems only come up when trying to
    duplicate part of the text of an extent.

Yes, that's right.

      Since the required behavior
    depends on the extent, we can't handle it automatically, and I just the
    `duplicate' property should thus be a function which will handle those
    "corner" cases.

You're just moving the unsolved problem inside the `duplicate'
property.  Nobody has ever proposed a good solution to this that I
have seen, so I think none exists.  If you can present one, that
will change my mind.  However, I will not agree to simply sweep
the problem under a hook and presume someone will solve it later.