Aye.
and different styles of humour. Irony in particular can look aggressive.
Almost anything written in a post rather than spoken face-to-face can be misinterpreted ... it's easy to underestimate how much influence body language has on our understanding of what's said.
Absolutely. Particularly since irony is a fast fading mode. Well, not so much irony fading but the true understanding of what it is, how it's used and what it communicates.
Emojis are a ham fisted attempt at filling in for the missing expression, body language and interpretive skills as well as compensating for the words left out in the post twitter world of brevity.
I find that accusations of "passive aggressive" behaviour often come from those more inclined toward emphatic speech and homilies.
It is a charge frequently laid upon responses that are calm and reasoned.