[bavila]

> An example is responding back to a message with "Ok.". I see many over, say, 50 do this much more often, but to many under, say 30, this is taken as very passive aggressive.

I can see how some might take a single "Ok." that way, but it probably really does depend a lot on context and the nature of the relationship. I tend to acknowledge most people's comments in a very mater-of-fact manner, but I feel adding a simple "thank you" (as in "Ok, thank you.") helps to dispel the raw bluntness of a plain "Ok."

"Please", "sorry", and "thank you"--these magic words can work wonders.