See comment on AdjustStringForLocaleDirection:
https://cs.chromium.org/chromium/src/base/i18n/rtl.h?l=105

> TODO(idana)  bug 6806 : this function adjusts the string in question only
> if the current locale is right-to-left. The function does not take care of
> the opposite case (an RTL string displayed in an LTR context) since
> adjusting the string involves inserting Unicode formatting characters that
> Windows does not handle well unless right-to-left language support is
> installed. Since the English version of Windows doesn't have right-to-left
> language support installed by default, inserting the direction Unicode mark
> results in Windows displaying squares.

This was referring to Windows XP. Now that we no longer support XP, we should be able to remove this exception, and generally improve RTL support.

See this code review comment:

https://chromium-review.googlesource.com/c/chromium/src/+/876522/5/base/i18n/rtl.h

> However, I think we don't have to worry about this any more because we don't
> support Windows XP any more and I believe Windows 7 or later does come with
> RTL/BiDi support out of the box regardless of the UI language of the OS. 
>
> We need a bit of testing, though.