`format' & strings w/ duplicatable extents

Shouldn't it be mentioned in the info and various docstrings that `format' (and all function which uses format), `set-keymap-prompt' and probably other functions don't even use duplicatable extents of strings? At least the docstring of `set-extent-property' should mention this (I could do it). E.g., with the following code, the keymap prompt is not in red, neither are the last two occurances of "string" in the minibuffer area: (let* ((string "string") (extent (make-extent 0 (length string) string))) (set-extent-property extent 'duplicable t) (set-extent-face extent 'red) (set-keymap-prompt ctl-x-map string) (display-message 'message (concat string (format string) (format "%s" string)))) - Christoph