Some IRCd's give different responses on a remote whois if the nick does not exist.
UnrealIRCd:
whois r4
:irc2.unrealircd.org 401 KindOne r4 :No such nick/channel
:irc2.unrealircd.org 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:irc2.unrealircd.org 402 KindOne r4 :No such server
Heavily? modified UnrealIRCd 3.2.6:
whois r4
:*.SwiftIRC.net 401 KindOne r4 :No such nick/channel
whois r4 r4
:*.SwiftIRC.net 401 KindOne r4 :No such nick/channel
InspIRCd:
whois r4
:bender.chatspike.net 401 KindOne r4 :No such nick/channel
:bender.chatspike.net 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:bender.chatspike.net 401 KindOne r4 :No such nick/channel
:bender.chatspike.net 318 KindOne r4 :End of /WHOIS list.
ircd-ratbox: (EFNet)
whois r4
:irc.servercentral.net 401 KindOne r4 :No such nick/channel
:irc.servercentral.net 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:irc.servercentral.net 402 KindOne r4 :No such server
charybdis: (fork of ircd-rabox)
whois r4
:Caprica.StaticBox.net 401 KindOne r4 :No such nick/channel
:Caprica.StaticBox.net 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:Caprica.StaticBox.net 402 KindOne r4 :No such server
ircd-seven: (fork of charybdis)
whois r4
:card.freenode.net 401 KindOne r4 :No such nick/channel
:card.freenode.net 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:card.freenode.net 402 KindOne r4 :No such server
bahamut:
whois r4
:laud.ix.us.dal.net 401 KindOne r4 :No such nick/channel
:laud.ix.us.dal.net 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:laud.ix.us.dal.net 402 KindOne r4 :No such server
u2.10.12.10+snircd(1.3.4a):
whois r4
:azubu.il.us.quakenet.org 401 KindOne r4 :No such nick
:azubu.il.us.quakenet.org 318 KindOne r4 :End of /WHOIS list.
whois r4 r4
:azubu.il.us.quakenet.org 401 KindOne r4 :No such nick
:azubu.il.us.quakenet.org 318 KindOne r4 :End of /WHOIS list.