Hello,
I'm having exactly the problem posted here with polylang and Persian wordpress but that topic has been closed:
http://wordpress.org/support/topic/language-direction-problem-rtl-ltr
I've installed English, Persian and Dutch in polylang. Persian shows RTL and it's correct, Dutch is also working fine and it's in LTR, but the English language shows as the RTL language! Settings are correct in Polylang.
Thanks for your support