I think it's likely Fritz both ranted about the parts he disagreed with and raved about the parts he loved over the years, and that both the diary and memoirs are reliable on this point.
Yes, this, because Dantal lists another Candide reading in September '85 and there he says that they finished the first part and then abandoned the second because Fritz didn't like it. :P
Re: Dantal: Dog Name, Reading, and other Details (1784-86)
Yes, this, because Dantal lists another Candide reading in September '85 and there he says that they finished the first part and then abandoned the second because Fritz didn't like it. :P