rcirc-nick-completion-format

rcirc-nick-completion-format is a variable defined in `rcirc.el'.
Its value is

"%s: "

Documentation:
Format string to use in nick completions.

The format string is only used when completing at the beginning
of a line. The string is passed as the first argument to
`format' with the nickname as the second argument.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.