It's wrong to do it on posts though. I have often responded to a comment with a rather heated reply before thinking better of it and hitting the Cancel button. I guess I like to vent but would rather my "venting" not end up in some site's DB.
Totally get it, and it is a problem. I don't like it, and I also don't like clipboard access. Browsers could have a mode that prevents this, similar to how certain features don't work unless a user has interacted with the page (like playing sound). Something like no queries when an input field contains data unless the user submits a form via a click or enter.
