My apologies regarding my less-than-tolerable knowledge of even the most basic facts about the Japanese language. I have to look it up…
Regarding BiDi/RTL: let me hastily say that yes, I do understand your hesitation to commit major efforts just to support something which might not translate into demand.
But look, even as it is, EmEditor correctly displays Hebrew, unless spell checking is ON. When this is so, it reverses the word order in the string, while each word by itself is still correctly displayed. Strange, but not really a major issue. Usually this is enough!
It is however practically impossible to edit Hebrew or even to select parts of it. What I do when the need arises is to select the whole string, sometimes with a bit of LTR text on either side, paste it to MS Notepad, edit what I need there and copy/paste it back. This too is tolerable most of the time.
So, take your time…