I'm jaded and cranky too, but thats why things don't bother me from a stylistic perspective. Relatively, fake politeness is more irritating to me.
>Also, if you see "polite" writing how would you know it's fake?
You develop your own detector after being "trained" on the dataset of prior comments.
To the larger point, this isn't about absolute certainty - which is a red-herring and an unattainable ideal.