instead of on NestedCommandIrcProxy.
ReplyIrcProxy._sendReply expects action=True to imply noLengthCheck=True, but only
NestedCommandIrcProxy.reply() enforces the latter, not ReplyIrcProxy.reply().
This crash was introduced in 3c1c4a69e9927bcc7265b1d77fd1ab49cb55090e by
moving NestedCommandIrcProxy's .reply() to ReplyIrcProxy.