Steps to replicate the issue (include links if applicable):

• Open Firefox, verify that in your preferences the font-size is 16px (default font-size)
• Logged in or logged out, open a random article on en.wp or fr.wp
• in editing mode, add some lines of text for testing different language codes, e.g. <span lang="frm">lorem ipsum</span>, <span lang="fr">lorem ipsum</span> and <span lang="mal">lorem ipsum</span>.
• then preview the article and look at the font size in preview mode
• test different font sizes in your browser, for exemple 10-12px, and when logged in test different appearences, like Vector and Vector 2022.

What happens?:

• Different language codes show different default font size, and not all languages are adapting in the same way when the font size of Firefox changes. In addition to this, Vector and Vector 2022 have different issues.

Vector 2022 and Vector 2010, with font size = 16, preview mode:

• text with some language codes has different font and font size (e.g. mal)

Vector 2022, with font size = 12, preview mode:

• text with some language codes is bigger (e.g. frm, tha, ukr, enm)
• text with some language codes is normal (e.g. fr and en)
• text with some language codes has different font and font size (e.g. mal)

Vector 2010, with font size = 12, preview mode:

• text with some language codes is normal (e.g. frm, tha, ukr, enm, fr and en)
• text with some language codes has different font and font size (e.g. mal)

Vector 2022 and Vector 2010, with font size = 12, text saved:

• text with some language codes has different font and font size (e.g. mal)

What should have happened instead?:
*When the browser font size changes, all texts with different languages should react in the same way in preview mode, both in Vector and in Vector 2022.

• Text in preview mode should look like the saved text.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):
(Discussion on fr.wp)

<span lang="frm"> is not used on wikipedia. This is just a simulation. The different font size for different languages affects articles using templates like Quotations (Citation, Traduction and Citation étrangère on the French Wikipedia).

Tested with Firefox Version 106.0.3 (64 bits), Windows 10 Home
Tested with Firefox, Linux