Re: enriched-mode and switching major modes.

[Richard Stallman]

    XEmacs's version of overlays (called extents) can be part of the text
    (which is a property they call `duplicable').  We could do the same.

We already did.  That's what text properties are.

The reason I decided that text properties should not belong to extents
which are objects is that there is no consistent way to preserve such
identities through cutting and pasting.  Every way of doing it, that I
could see, gives inconsistent behavior in some cases.  That I do not
want.

If you can design a system to attach text properties to extent objects
that gives consistent behavior, I would not object to implementing it.