We've sometimes thought about tracking and showing the edit history of HN comments, but I think this is one place where (let's call it) over-surveillance could lead to more harm than good. Certainly some users abuse editing, but there are also many cases where it's important to let people save face, give them an out, and so on. HN is supposed to be a community and it's important for communities to be forgiving. A certain degree of forgetfulness creates greater ease and freedom. No one wants to be around a superintelligent flaw-pointer-outer. So I think an edit history tracker would have unintended consequences and on balance is probably a bad idea.