Some small tips on IRC (tested on freenode)

Ok now your nick is Guest42666 and whe nyou try to do:

/nick MyNick

You get:

Nickname is temporarily unavailable

This is a border effect of the enforce parameter. To get everything back:

/quote NickServ identify MyNick MyPassWord
/quote NickServ set enforce OFF
/quote NickServ release MyNick MyPassWord
/nick MyNick
/quote NickServ set enforce ON

And you are good to go chatting!

Reference: https://michielvwessem.wordpress.com/2010/02/01/irssi-freenode-nickname-temporarily-unavailable/