"Alexander Schroeder" <ASC(a)bsiag.com> writes:
(put-nonduplicable-text-property start end 'face nil)
(put-nonduplicable-text-property start end 'font-lock nil))
That looks as if all face text properties are removed, just like in
Emacs.
Text properties, yes. But not all extents. Text properties are
implemented using extents, but not all extents are those created by
the text properties compatibility layer.