The browser is a beta, and very limited. A kobo Vox might be a better choice for reading on the web.
I am clueless about right to left languages, but i do know that you would have to install the proper font set. I'm guessing that the device doesn't know or care what direction people read in--so if the book is properly converted into an ePUB, from a device point of view, it's all just bits.
An earlier post on MR confirmed that the Touch supports Hebrew--another right to left language.
https://www.mobileread.com/forums/showthread.php?t=83405