You are suggesting that we let the font and the shaping engine decide
which alternative to use? That sounds un-Emacsy to me. For the use
case where only specific characters should be affected, I think we
should have a facility whereby users could specify, for each character
that has alternatives, which one to use.

No, I am not suggesting that every variation has its own tag and the user can choose which tag they would like or not.

For example look at the FiraCode variations attached

On Sat, Sep 24, 2022 at 6:31 PM Eli Zaretskii <eliz@gnu.org> wrote:

> From: समीर सिंह Sameer Singh <lumarzeli30@gmail.com>
> Date: Sat, 24 Sep 2022 18:15:23 +0530
> Cc: emacs-devel@gnu.org
>
> I don't understand: how does this handle the case where a certain
> character has more than 2 alternative glyphs? which alternative will
> be selected?
>
> I was answering this question, I thought you were asking what would happen if we pass multiple tags for the
> same glyph.

You are suggesting that we let the font and the shaping engine decide
which alternative to use? That sounds un-Emacsy to me. For the use
case where only specific characters should be affected, I think we
should have a facility whereby users could specify, for each character
that has alternatives, which one to use.