FWIW, I added corrections to the claims made by wsmwk (Thunderbird Team) and a summary of the feedback from this thread to Bug 1802813 comment 4 at the time they added their comment.Even thought the reasoning behind the removal of CSV export was faul...
> I don't know, why a good working function gets deleted for no reason.Bug 1226851 (reported 2015-11-21; actioned 2021-08-14) answers this question: someone thought that "known limitations" of the export were sufficient reason to remove this feature....
