So the issue is that user interface language should not effect how language is displayed.
If you are reading a thread for example in English, but in a RTL language, the English should be aligned to the left, regardless to the interface.
Same goes for reading an RTL language in an English interface.
The is the expected behaviour in all RTL sites.
To give you the idea, I am attaching here an image of the FAQ when viewed from the Hebrew interface.