Eric Stevens
In the context of the present discussion, the question is, does the conversion to Lab colour incur any more damage than one can expect in the course of ordinary editing? My understanding of nospam's claim is that it does. My (admittedly limited) experience with it suggests that conversion to Lab causes no significant damage; certainly less than I am going to inflict on the image by the changes I want to make.

Martin Brown
Since CIELAB is a colour space intended to manage just noticeably colour differences more optimally than the naive RGB colour space it isn't too surprising that you cannot *see* a difference in the final JPG taken from RGB or via CIELAB. But they are very slightly different.

Eric Stevens
Agreed, but the question is, does the difference matter? In particular does it matter enough to earn the reputation that nospam is trying to assign to it? I would generally answer 'no' to both of thos questions.