Entering some spaces at the start doesn't clear up all the artefacts.

>> For instance, see bug#51385 where they have a weirdo font that maps
>> "[TRACE]" (and 260 other strings) to different glyphs.  We need that
>> list, because we certainly don't want to be passing "[TRACE]" to
>> harfbuzz when not using that font.
>
> I think we rather need to have a (minor) mode which uses those, and
> under that mode we do want to pass these strings to HarfBuzz.  If the
> default font doesn't support the corresponding ligatures, we display
> the literal strings.  It is then up to the user to install the right
> font and tell Emacs to use it (via some face, I guess).

Yes and no.  There's no limit to the number of these strings that fonts
support, so if this hypothetical minor mode were to "list them all",
it'd basically be the same as running all text through harfbuzz.  Which
we don't want to do in general.  Ergo the need to have a per-font
ligature table.

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