Subject: Re: bug#18017: 24.4.50; Isearch case sensitivity broken/confusing

From: Juri Linkov <[email-masked]>
Date: Tue, 15 Jul 2014 00:17:45 +0300

> Type this in buffer *scratch*:
>
> Add
> add
> ADD
>
> M-x set-variable case-fold-search nil
>
> C-s add C-s
>
> C-s M-c C-s
>
> The M-c says that search is now case-insensitive, but the second and
> subsequent C-s's do not find occurrences Add and ADD.
>
> C-s add C-s
>
> That finds all three (case-insensitive).

Did you mean `C-s M-c add C-s' in the last key sequence
(that finds all case-insensitive)?  You have to use M-c to toggle
case-sensitivity for case-fold-search that you set to nil.
And `C-s C-s' naturally restores case-sensitivity of the
previous search string, but it's possible to configure this
using `isearch-keep-mode-variables' from bug#11378.