It is true that arguments don't change and should be examined from their own qualities, but people are generally irrational and attach importance, implicitly, t

It is true that arguments don't change and should be examined from their own qualities, but people are generally irrational and attach importance, implicitly, to meta-data. If I am an author and I put a note saying "this is not my point of view anymore", and you cherry-pick a quote like nothing changed, this is misleading because, willingly or not, this is an appeal to authority. Just as if someone was on your side saying "I approve what you say". The subtext is different if that person actually says "I once thought the same thing as you, but this was wrong and naive". I would expect a simple "take this blog post (note: author changed his mind since then) and replace...". Or maybe just write down your own version of the argument, with your own words.