While working on tool for online translating, I should have probably expected this, but somehow it surprised me - Weblate should support RTL languages.
This issue was brought to me today by Yaron Shahrabani (Hebrew translator of Wine) and I simply had to look at this quite unexplored area for me. Fortunately it seems to be pretty easy, just matter of adding few html attributes to right places.
I've quickly adjusted the code (the hardest thing was to get list of RTL languages) and Weblate should now properly support RTL languages on both sides - as an user interface language and as a translated language.
In case you understand any of Arabic, Farsi, Hebrew, Urdu or other RTL language, I'd really like to hear from you if Weblate shows them correctly.