The only other problem then is receiving back messages I *send* which I believe is what you're referring to in your edits and the other filed report(s). Sending messages to myself means that the scripts process on the first received message and also on the echoed copy of sending it. Duplicated messages also appear in the playback, if you handle that separately.
When echo-message is enabled, mIRC will filter out echoed messages, so scripts should never see them, unless they are using on PARSELINE.
In the next beta, I will be adding an on PARSELINE identitifer $parseem that is set to $true if mIRC thinks the incoming line is an echoed message.