I’ve had one other request for it, but it needs the votes to get it prioritized.
Feedly supports RTL languages, however it’s a proprietary product (closed source) and that’s enough for me not to use it.
Commafeed in the other hand is a free viable alternative with good right-to-left support, although it may lack some of the features of Newsblur.
I really hope to see RTL support in Newsblur too, but until then I’d suggest RTL users to give Commafeed a try.