Be the same person in the comments that you are at the lunch table.

Distance makes people bolder, and a screen removes the face that would normally stop you mid-sentence. The version of you that types things it would never say aloud is still you, and the gap between the two is where most regret gets manufactured. One personality is simpler and cheaper to maintain than two.

Read anything you are about to post as though the person were standing in front of you. If you would not say it that way, rewrite it or drop it entirely. That single filter removes nearly everything you would later want deleted.