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

• Enable "Universal Language Selector rewrite" beta feature on Preferences.
• Enable SidebarTranslate gadget
• Open any English Wikipedia pages, for example https://en.wikipedia.org/wiki/Chocolate
• Click on the language portlet ("XX languages" button on the right side of the article title).

What happens?:

• Notice that for language names that are displayed in non-Latin scripts on other Wikipedias (ULS rewrite beta feature is also enabled), but displayed as corresponding English names on the English Wikipedia, such as "Japanese", "Arabic" and "Persian", these English language names are displayed with the non-Latin scripts language flavour. It is observable that typical Japanese wide characters were used for the "Japanese" language label, whereas the "Persian", "Arabic" and "Chinese" labels seem thinner and positioned lower than let say, "Malay" or "Indonesian" labels.

What should have happened instead?:
If the language name is localized to English, then the styling for localize language name labels should be shown in English.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):