Please keep in mind that the Forum plugin was developed by a user who is no longer active in the Geeklog community. We (as in: the Core team) only provide minimal support for it at the moment to ensure security issues and such are fixed in a timely manner. We are not intimately familiar with the code - if something doesn't work, I, for example, don't immediately know where or how to fix it. We can only hope that someone in the Geeklog community will be picking up support for the plugin eventually.
Also, the majority of Geeklog sites are running on languages that are written left to right - there simply isn't a lot of knowledge about RTL languages in our community. You've been pointed to LWC before - he's the only active user that I know of who's running sites in an RTL language.
From personal experience, trying to address LWC's occasional bug report about RTL support in Geeklog itself, I find that I'm having a hard time figuring out what's right and what's wrong. I'm simply not familiar enough with RTL languages to know how something is supposed to work or look.
And of course you shouldn't forget that Geeklog is a project run by volunteers. We are all doing this in our spare time. I'm sure someone could figure out what's wrong with the forum and RTL languages, but what's in it for them? I think I pointed you to our list of users providing Paid Support
before. Would that be an option?