bug#32651: flyspell marks doublons when not the same case

[Eli Zaretskii]

> From: Reuben Thomas <rrt@sc3d.org>
> Date: Thu, 6 Sep 2018 20:16:10 +0100
> 
> Flyspell marks for example the second "AND" in "an AND split and AND join" as 
> a duplicate.
> 
> This seems to be deliberate: in line 1153 of flyspell.el (on current emacs-26 
> branch)
> flyspell-word-search-backward is called with IGNORE-CASE set to t.
> 
> I don't understand this: if it's not the same case, it's probably deliberate, 
> no?
> 
> I checked that simply removing this `t' argument makes doublon detection work 
> as I'd expect: "AND AND",
> "and and" and "And And" are all marked as doublons, but anything that's not 
> the same case isn't.

There are valid use cases where the current behavior is what the users
want (e.g., "And and" at the beginning of a sentence).  So we could
introduce an option to do what you want, but I don't think we can
change the default behavior unconditionally.