bug#40216: 28.0.50; Misinformation in isearch char-fold

[Juri Linkov]

>     >> Do we need an option to char-fold-regexp that says 'only apply
>     >> char-folding to non-ascii characters'?
>
>     Eli> But this feature is not intended only to find variants of non-ASCII
>     Eli> characters when one searches for a non-ASCII, it is also intended to
>     Eli> find variants when searching for ASCII characters.  For example,
>     Eli> searching for a is supposed to find ä and à and á.  Or am I missing
>     Eli> something?
>
> Yes, thatʼs exactly right. But in the case where you have mainly
> characters where you donʼt want case-folding, it might make sense to
> restrict the folding to non-ascii as an optimisation. eg. Suppose my
> name were Røbert, with people frequently misspelling it as Robert, I
> might want isearch to just search for "R\\(?:ǿ\\|[øǿo]\\)bert"

I tried to find Røbert by typing Robert, but char-fold fails to find it.
A bug in char-fold?