[FIG[
[FIGCAPTION[
[1] [CITE@en[RFC 1459 - Internet Relay Chat Protocol]] ([TIME[2014-03-28 11:47:07 +09:00]] 版) <http://tools.ietf.org/html/rfc1459.html#section-2.2>
]FIGCAPTION]

> Because of IRC's scandanavian origin, the characters {}| are
considered to be the lower case equivalents of the characters []\,
respectively. This is a critical issue when determining the
equivalence of two nicknames.
]FIG]

[FIG[
[FIGCAPTION[
[2] [CITE@en[RFC 2812 - Internet Relay Chat: Client Protocol]] ([TIME[2014-03-19 19:49:44 +09:00]] 版) <http://tools.ietf.org/html/rfc2812#section-2.2>
]FIGCAPTION]

> Because of IRC's Scandinavian origin, the characters {}|^ are
considered to be the lower case equivalents of the characters []\~,
respectively. This is a critical issue when determining the
equivalence of two nicknames or channel names.
]FIG]

[FIG[
[FIGCAPTION[
[3] [CITE@en[RFC 2813 - Internet Relay Chat: Server Protocol]] ([TIME[2014-03-08 23:19:56 +09:00]] 版) <http://tools.ietf.org/html/rfc2813#section-3.2>
]FIGCAPTION]

> Because of IRC's Scandinavian origin, the characters {}|^ are
considered to be the lower case equivalents of the characters []\~,
respectively. This is a critical issue when determining the
equivalence of two nicknames, or channel names.
]FIG]