> > Another consideration (for me, at least): I think (and hope) that
> > eventually users will be able to have multiple such lists (sets)
> > of char mappings that they can choose (and mix and match - sets of
> > such sets, for different purposes/contexts).  IOW, I don't see just
> > a single set of ad-hoc char mappings.  But this is anyway for the
> > future.
>
> Yes, we have to take into consideration that in addition to the
> plain customizable list we are adding to the next release,
> in later versions we might also add more customizable lists,
> e.g. with categories and other character groups.

One possibility is to (now), instead of having an option with a single list of ad-hoc mappings as value, have an option with an alist of such lists as its value, where the car of an alist entry names the particular ad-hoc mapping.

See my suggestion in an earlier mail in this thread.

> >> Another thing we need to do is to allow customization to remove
> >> default mappings.  Maybe this is possible by using the same
> >> defcustom with a rule like: remove default mappings when a char
> >> is mapped to an empty list, e.g.
> >>
> >> - adding more mappings for ‘`’:
> >>   (defcustom char-fold-ad-hoc '((?` "❛" "‘" "‛" "󠀢" "❮" "‹"))
> >>
> >> - removing default mappings for ‘`’:
> >>   (defcustom char-fold-ad-hoc '((?`))
> >
> > Yes, I would think that would work (already).  But I could be wrong.
> >
> > Thanks for taking a look at this.
>
> After long-planned terminology improvements, I'd wait for sync between
> branches to avoid merge conflicts, and then I'll submit a patch taking
> into account all opinions about the default value for users who will
> enable this feature in the next release.

Sounds good. Thx.