Earlier quoted context omitted.
Respectfully, it is important to understand whether sort stability is as bug or not. Particularly since you seem to have experienced exceptions on Android, and assuming that the problem was in the sort stability may have mislead you.
It's still reproducible just by substituting the top function for the stable alternative we use: http://pastebin.com/D3S6SYBM . Haxe 3.1.3 on OSX.
I'm not dismissing the existence of a bug just because of this (although the issue may be related to it), but non-deterministic comparison functions are problematic with many sort _algorithms_. You might experience (other) problems when using implementation independent "sort" APIs, since many algorithms need to rerun the comparison function several times and expect consistent behaviour; I would expect certain algorithms to, for instance, never complete.