For starters: I'm not criticizing your bug report here - I think you make a fair point and I am impartial to the outcome. However, I think that a bit of clarification is in order..
Yes - I accept that the IRC RFCs may specify usernames up to 9 characters
They do not. The people in that old thread confuse nicknames and usernames, drawing an incorrect link between the two. They are fully independent.
Technically, the RFCs (1459, and 2812 if you care about IRCnet in particular) define the username length as being unbounded. The widely accepted de-facto standard username length limit is exactly 10 characters, however. No more, no less. There are virtually no networks with username length limits other than ten characters. mIRC currently follows this de-facto limit as well.
1. mIRC itself allows userids of up to 10 characters on the IDENT options page. $address(nick,5) works on these, but $address(nick,6) still truncates the first character.
Given the above limit, that makes perfect sense.
2. As stated in that link, the RFC states "While the maximum length is limited to nine characters, clients SHOULD accept longer strings as they may become used in future evolutions of the protocol." and mIRC doesn't follow this.
This is again referring to nicknames. See above: one could argue that mIRC is not following the RFCs, but it is not this statement that is relevant.
4. Perhaps, as mIRC already does in many other cases, mIRC needs to have adjustments to work with real-life servers which are outside the formal spec in minor ways like this.
I don't disagree, although I think it's also rather stupid for those servers to mess with well-established de-facto standards. Such changes are likely to cause problems with more than just mIRC.
