this did not occur before update. only after update.
only firefox. not libre wolf, not ungoogled.
there's more pics in the same vein. pics are of general webpage reading.
Firefox default font was Noto Serif.
Changed it to Noto Sans. Still messed up.
Changed all of FF to Droid Sans and problem SOLVED.
Conclusion? Broken Noto? sudo eopkg check
says all Notos green OK.
posted for posterity. maybe its related to somethin else?
and for anybody who opened FF today and their default stock fonts wigged out.
ps- this didn't happen in Budgie, FF, post-update, last night. Relevant?