if i know someone in person, or at least have developed a deeper online relationship (through remote collaboration for example) i am going to treat time like i would in person, whereas if i don't know them as i don't know you it becomes much easier to say "you are wrong!" because i don't have to fear your negative reaction. as you say here, anonymity allows for a certain boldness
i occasionally find my self starting a comment on hn with "that's wrong" but once i write the actual explanation i realize that i can make my point without that aggressive lead, so i remove it. and then i go over the text and see where i can reduce the boldness without weakening my argument, for example by prefacing statements with i feel or i believe or i understand instead of stating them as absolutes or indisputable facts.
but this is usually a second editing step that i have to consciously think about. though maybe after doing it often enough, it can become a habit or second nature to my writing