Lets use this thread to investigate RTL and LTR problems.

"interface language" is the language specified in the user options.
"page content language" (Wiki Language) is the language of the wiki specified during setup

• Test 1:

Interface Language : EN
Wiki Language: EN
Writing arabic in scribe:

Results:

• Test 2:

Interface Language : AR
Wiki Language: EN
Writing arabic in scribe:

Results:

Still broken

Conclusions:
Visual editor language follows the Wiki installation language (page content Language).