It is increasingly common for IRC channels to be “bridged” onto other networks such as XMPP, Matrix, etc. Sometimes the software does a good job at mapping each non-IRC user into an IRC user, but more often than not it doesn’t. In that case you might receive a message like:
09:47 <bridge> <john> I am not on IRC
where ‘bridge’ is a bot responsible for sending messages back and
forth between networks, and ‘john’ is the user name of someone on
a different network. Note that the bot indicates this within the
message (<john> I am not on IRC) that appears in your chat
buffer.
If this annoys you, the user option rcirc-bridge-bot-alist may
be of use. It consists of descriptions of what users are these kinds
of “bridge bots” and how they format their messages. To handle the
above example, we might set the user option to:
(setopt rcirc-bridge-bot-alist
'(("bridge" . "<\\(.+?\\)>[[:space:]]+")))
If there is an entry for the current user, rcirc will take the
associated regular expression and try to find a match in the message
string. If it manages to find anything, the matching expression is
deleted from the message. The regular expression must contain at
least one group that will match the user name of the bridged message.
This will then be used to replace the username of the bridge bot.