Hello,
Well, actually, it seems that I did not understand anything at all :-)
Sorry about that, but I am new to the source code, and it is not very clear to me.
So if I try to summarize what I have got:
- In the past, what I could see with the standard 'M-x fill-region' over paragraphs or lists with empty lines between each inner items, was probably performed thanks to several calls to org-fill-paragraph. Removing the org-fill-paragraph-separate-nobreak-p function simply highlights that I was fortunate to use it this way before, and there is just no org-fill-region.
- There are no unit tests, nor past discussions about how different text block contents should be filled with this new function