It is hard. A comment has to be in a pretty narrow window for me to engage in discussion. If something is adjacent to or just outside of my understanding I may choose to engage in discussions where one or both of us learn something.
There are a few areas where I am an expert and may chime in with corrections or additions to generally good comments and discussions.
If a comment is perfectly in alignment with my thoughts I may say so but that is not a productive conversation, more a symbol of fellowship.
If a comment is too far out of agreement I am not going to engage. From past experience this will never yield fruit. Either it will turn into a flame war, a perpetual chain of disagreements until one of us gives up, or getting downvoted to oblivion by a brigade who disagrees with me.
Productive discourse needs a safe space, and online is NOT a safe space.