Too many times I have spent five, ten, or even fifteen minutes writing some long response to some comment spontaneously or as part of a conversation, only to attempt to hit the "Preview" button (to review for spelling and grammatical mistakes) only to hit the "Cancel" button instead and have the entire message wiped away, irretrievably, thus forcing me to rewrite everything.
If there were simply an "Are you sure?" pop up, like there is when one tries to delete one's own comment, this would not be an issue at all. It is the fact that a simple mis-click can
cause so much pain have such a permanent and undesired effect that I think this is worthy of a report here (as a BUG, rather than as an idea).
That is all.