Variable: erc-query-on-unjoined-chan-privmsg
erc-query-on-unjoined-chan-privmsg is an alias and customizable for
erc-ensure-target-buffer-on-privmsg, defined in erc.el.gz.
Value
t
Documentation
When non-nil, create a target buffer upon receiving a PRIVMSG.
This includes PRIVMSGs directed to channels. If you are using an IRC bouncer, such as dircproxy, to keep a log of channels when you are disconnected, you should set this option to t.
For queries (direct messages), this option's non-nil meaning is
straightforward: if a buffer doesn't exist for the sender, create
one. For channels, the use case is more niche and usually
involves receiving playback (via commands like ZNC's
"PLAYBUFFER") for channels to which your bouncer is joined but
from which you've "detached".
Note that this option was absent from ERC 5.5 because knowledge of its intended role was "unavailable" during a major refactoring involving buffer management. The option has since been restored in ERC 5.6 but now also affects queries in the manner implied above, which was lost sometime before ERC 5.4.