erc-current-nick-highlight-type

erc-current-nick-highlight-type is a variable defined in `erc-match.el'.
Its value is

keyword

Documentation:
Determines how to highlight text in which your current nickname appears
(does not apply to text sent by you).

The following values are allowed:

nil - do not highlight the message at all
'keyword - highlight all instances of current nickname in message
'nick - highlight the nick of the user who typed your nickname
'nick-or-keyword - highlight the nick of the user who typed your nickname,
or all instances of the current nickname if there was
no sending user
'all - highlight the entire message where current nickname occurs

Any other value disables highlighting of current nickname altogether.

You can customize this variable.