File CSS is flipped if the direction is RTL. Site CSS is flipped if the direction (ltr/rtl) is different from that of the wiki content language. While this didn't make any difference in 1.17, since 1.18 (see r91518 et al.) it causes flipping. This implied that all site CSS should be checked for rules that need @noflip. I think it makes much more sense to *not* flip site CSS by default, because most style is for content stuff which should not depend on wgLang direction. This is easily changeable in either ResourceLoaderSiteModule or ResourceLoaderWikiModule (?) by adding getFlip() { return false; }, but this would likely require something like @flip or @doflip in CSSJanus (which would behave the other way around as @noflip).
(Relevant revision: r84740)
Version: unspecified
Severity: normal