At this point in the discussion, I'd like to ensure that people commenting have read the suggested spec, as some comments coming through suggest they haven't.
In particular, it does say that messages should be clearly marked. It makes no suggestion about changing any chat transcripts that a client stores. It says that clients may be able to advertise that don't support (or rather, not advertise that they do support) editing of messages older than the most recent. Thanks. /K
