I think the OP is referring to the fact that before Sierra, if you were using a language that is written right to left, the rest of the OS X UI still went left to right. With Sierra, I believe the UI now also goes right to left. Some people got used to the LTR UI with the RTL language and don't like the change.
(If the OP meant something entirely different, then ignore all this and I will slink on out.)