Mark post as superseded or out-of-date
Add an option for users to mark their own posts as "superseded" and mark the text with a strikethrough or similar.
Some people on my team delete their early posts or replies if, after having a discussion, we change our minds and decide to go a different direction. They delete the posts because they don't want someone to read it later and draw an incorrect conclusion. But it would be less ambiguous if we could keep the conversation history (i.e. not delete it) but allow the author to mark the post as "superseded" or "out-of-date."
Ron Allen commented
Great use for basic AI or even fundamental thread watching like in Outlook "YOu are not responding to the most current message in this thread"