Forums Bug Reports on *:parseline:out:*: has trailing $lf

Yes - but that doesn't mean that it should be returned as part of $parseline.

According to IETF RFC 2812, all messages should be terminated by $CRLF, not $LF. So if I agreed with your logic, then I would expect $parseline to end with $crlf not just $lf. (It seems very odd to strip the penultimate $cr character and leave $lf. It also seems inconsistent for ON PARSELINE IN lines not to have a trailing $lf.)

My point, however, is that this is both unnecessary (because you can assume that the message sent to the server was terminated by a $LF or $CRLF), but also counter-intuitive (since every other example in mIRC does not include a trailing $lf) and confusing (because the $lf is invisible).