I dunno... If i decide not to go forward, and not to write any message at all (and at the same time, i have already quoted someone's message), i just delete (manually) all symbols in my message (including the quoted message). It means, that formally, i started the message, but after deleting everything, the only thing that's left, is cursor in the message field. I hope it's not a big deal, that i put my cursor in an empty field (i also do it sometimes by accident, when i touch an empty field with my fat fingers while reading someone's message).