RE: char equivalence classes in search - why not symmetric?

[Drew Adams <drew.adams@oracle.com>]

> Because having both input characters mean the same thing
> uselessly deprives the user of expressive power.

Examples/arguments/reasons, please.  IOW, prove it.

You can always toggle char folding, just as you can toggle
case folding.

IMO, more users have been tripped up than helped by the rule
that "An upper-case letter anywhere in the incremental search
string makes the search case-sensitive." (emacs) Search Case.

Letting a user toggle between matching chars one-to-one and
matching chars according to equivalence classes, is sufficient
and clear, IMO.  Adding rules on top of this is not helpful.

But I would not oppose the current behavior as an option.
Let users decide whether matching is symmetric or asymmetric.

Maybe even let users toggle, or cycle among these two folding
(one-many) behaviors and unfolded (one-one matching) behavior.

> > Why not?  Why, when char folding, treat plain a specially for
> > searching?  Why not treat á, a, à, ã, ª, â, å, and ä the same?
> 
> For exactly the same reason.

What reason?  Please show how this optional matching
behavior "deprives the user of expressive power".