Exclude ircu2 and fill in the spec

Makefile

@@ -63,6 +63,7 @@ INSPIRCD_SELECTORS := \
 # statusmsg tests fail because STATUSMSG is present in ISUPPORT, but it not actually supported as PRIVMSG target
 # testKeyValidation[empty] fails because ircu2 returns ERR_NEEDMOREPARAMS on empty keys: https://github.com/UndernetIRC/ircu2/issues/13
 # testKickDefaultComment fails because it uses the nick of the kickee rather than the kicker.
+# testEmptyRealname fails because it uses a default value instead of ERR_NEEDMOREPARAMS.
 IRCU2_SELECTORS := \
 	not Ergo \
 	and not deprecated \
@@ -73,6 +74,7 @@ IRCU2_SELECTORS := \
 	and not statusmsg \
 	and not (testKeyValidation and empty) \
 	and not testKickDefaultComment \
+	and not testEmptyRealname \
 	$(EXTRA_SELECTORS)
 
 # same justification as ircu2

irctest/server_tests/connection_registration.py

@@ -169,7 +169,11 @@ class ConnectionRegistrationTestCase(cases.BaseServerTestCase):
         -- https://defs.ircdocs.horse/defs/numerics.html#err-needmoreparams-461
         -- https://modern.ircdocs.horse/#errneedmoreparams-461
 
-        Use of this numeric: TBD https://github.com/ircdocs/modern-irc/issues/85
+        Use of this numeric:
+        "The minimum length of `<username>` is 1, ie. it MUST not be empty.
+        If it is empty, the server SHOULD reject the command with ERR_NEEDMOREPARAMS
+        (even an empty parameter is provided)"
+        https://github.com/ircdocs/modern-irc/issues/85
         """
         self.addClient()
         self.sendLine(1, "NICK foo")