In attachment 101757 [details], you can see in the arabic UI with RTL on, that increase indent is on the left and decrease is on the right, which is incorrect for a RTL UI user. In the english UI with RTL, it is fine.
I had tested this on 4.1.6, 4.2.5 and 4.3.0.
Sorry my bad. I thought increase ident was the first icon in the english UI. :)