This is the reason that I really want it:
https://jsfiddle.net/hbdurdLb/
There is 2 bugs in a small CSS file:
1. In LTR the tag "<hr> does not appear above the arrow.
2. In LTR the border color of "h3" tag totally in green
Press on "Switch text direction between LTR and RTL" button to see the changes.
I can make it works!
But... Think about it, Flarum's system will support in themes.
It's not possible to create an perfect RTL extension by using overriding the original CSS.
Let me back, It's possible, But there is lots of work to change it for every theme that created.
If the BuildClientView are made problems, Maybe I can make an automatic LTR to RTL extension (for any theme/extension will be installed) that will be gain different access like merge with the core?
What do you say?
@Franz @luceos