I guess, we have no influence on the way, how FCKeditor implements this feature So, I see nothing we can do here.
Hiding the button is not a good idea. Many customers will be satisfied with the way the "Paste from Word" button works.
The toolbar configuration for FCKeditor is now located in a separate file, so customers can customize available buttons according to their needs.

I have tested with the demo on FCK site, and got the same behavior that you get (missing image)
Then, I have tested using IE as I did during while testing Jahia, and this time, the table of content is well present, but with some broken links.
I don't know what we should do, but whereas the broken links could be considered as a minor issue, the "missing image" is more problematic. Maybe we should deactivate the button on firefox (is it possible?)

I have also tried to paste my content, without specifiying it is some word content. This time, my table of content is well displayed (firefox). But it has not been automaticaly detected that it is some word content as it is done on IE (popup asking if I want to clean the pasted code). So it seems that the problem occurs during this cleaning, on firefox.

With my tests, I do not get any table of content (summary) at all - just a missing image placeholder instead
What is the expected behaviour?
I get the same behaviour also on the http://www.fckeditor.net/demo , so I do not know, what should we improve on our side? thanks!