In episode 4, Prarie/The OA meets Khatun again, she appears to have little bumps which look like braille.
This is a longshot but can anyone read any of this?
A high resolution version can be seen here
It's just been pointed out (thanks @user1118321) that there is also braille on the father's face also, I think this one is too difficult as the face is small relative to the screen:
This reddit thread seems to think it maybe who if then because and angel but it's ambiguous for the father:
by user philaj9
Ok here's what I have so far: The braille is in German. The top row on Khatuns forehead says "wer wenn' which translates to 'who if'. I can't figure out the bottom row on her forehead. Her right cheek, left screen I can see only close to her nose. Top says 'denn' or 'because' and bottom says 'engel' or ' angel'. Left cheek, right side of screen, I can only see another 'engel'. For the dad, I can only make out his right cheek, on the left side of the screen to say '5 as leere jene' which according to Google translate is '5 as empty ones'. I've been seeing a lot of braille characters that I just can't find in any alphabet online, one in particular that looks like the bottom right angle of a square. Hope this helps.
** UPDATE 3 **
Seems there is more braille here on the wall (thanks @starry for pointing this one out):