Nothing in the panel (Nor in other KF5 applications) got reversed if the language chosen is a RTL language. I've tried the --reverse option on PlasmaShell, It works good but the Kickoff and the notifications widget didn't got reversed (I didn't tried others "if exist"). Could it be that this [1] issue is affecting Plasma? 1: https://bugreports.qt-project.org/browse/QTBUG-43447
--reverse makes a difference here. Not claiming it's all correct, but the panel contents are clearly the over way round (latest 5.4 branch of qt)
here too some things are correctly reversed (panel and toolboxes are correct, systray incorrect, kickoff incorrect) It would perhaps be more useful a report per applet for those that don't flip correctly
But we should solve the problem in the panel first right?
I think this should be resolved in Qt 5.5, The upstream bug got resolved. You can close this for now. If I saw anything wrong in Plasma built with Qt 5.5 I'll say it.
Unfortunately, the bug still exist in Plasma (and KF5 as well) even after applying the fix in the upstream bug.
From QT 5.6 the RTL Works. more info in https://bugs.kde.org/show_bug.cgi?id=362326