Q: Why does irssi crash when pressing Ctrl-4?
A: Most unices are usually configured to send SIGQUIT to active process when
   Ctrl-\ is pressed. Some terminals also treat Ctrl-4 and Ctrl-\ equally, so
   Irssi will die to SIGQUIT. Two ways to fix this: change it to something 
   else with stty (stty quit undef) or in irssi /SET ignore_signals quit