Do we really need to know when a message was edited ? So what ? People make mistakes and there are plenty of typos along the way. Are we being audited by some government agency that needs to keep track of edits ?
This is a feature on some sites that use this platform, not on others, so apparently it can be turned off. The intent, I think, is to stop people from changing their previous posts invisibly in arguments. Mixed feelings about it, something to be said on each side of the issue.