"Swift completion" is relative to the game, not the community

[Nestama]

I mean if you say anything in game, you can get banned/reported, even if said nicely because the person "didn't want any unsolicited advice".

And yet I have not been banned for giving unsolicited advice...
While "expressions that compel a playing style" is mentioned in prohibited behaviour, it's specifically under "Offensive Expressions," which to me says if you're rude/mean with your advice (swears, slurs, insults) then you risk a ban. So if you want to tell a RDM that just spamming Jolt isn't how to play RDM, or a tank doing a single-target rotation in a pack of mobs (inevitably having them go after the healer, which could fall under nuisance behaviour or MPK) should AoE, you shouldn't/won't be banned if you're neutral/nice about it.