allout-overlay-interior-modification-handler is a compiled Lisp function in `allout.el'.

(allout-overlay-interior-modification-handler OL AFTER BEG END &optional PRELEN)

Get confirmation before making arbitrary changes to invisible text.

We expose the invisible text and ask for confirmation. Refusal or
`keyboard-quit' abandons the changes, with keyboard-quit additionally
reclosing the opened text.

No confirmation is necessary when `inhibit-read-only' is set -- eg, allout
internal functions use this feature cohesively bunch changes.