I noticed, that my clock is delayed for more than 1 minute in my computer (it should be synced with NTP however). And this cause wrong order of created comments in tasks.
I know, that you must rely in some places on users' time (for e.g. relativeness of time - "30 sec ago"), but I think ordering shouldn't be.
tl;dr: set your clock 1-2 minutes to past time (go back), and try create some comments in task.