I didn’t go farther with that patch because I only needed some of the add on’s functionality.
For example I don’t need to try to identify the parent of the object, and I don’t need to worry about Archetypes or old Python.
In my case since the Note content type is folderish. I create the extracted image in the note, which triggers another ObjectModifiedEvent, and so on until I hit the maximum number of recursions… the answer was to set a value in the request and check for it and stop if it is set.