when replying that way in any way, on text or actually just saying “cool”. my friends say cool a lot and I really don’t mind it and my partner says it too but some people have thought it was rude and I had a friend say “that’s what I say when I don’t give a damn”.
To be fair, I am also a millennial, but most of my friends were surprised when I told them about that correction I received from the younger generation. I guess that says more about my friends than millennials overall lol
I’m also a millennial, and I think it depends a lot on rapport as well. If you regularly talk with someone in text form, and consistently use punctuation, it probably doesn’t come off as passive aggressive than if you suddenly respond with the trailing period. It also probably makes one-word responses a lot more abrupt.
I agree with above, replying “Cool!”, or “That’s cool!” would likely go over much better in that context