doc/modes.txt

   1 Standard user modes are listed in help/opers/umode
   2 Standard server notice masks are listed in help/opers/snomask
   3 Standard channel modes are listed in help/opers/cmode
   4
   5 The sgml docs have more detailed descriptions.
   6
   7 User mode +x (hide hostname) is provided by contrib/ip_cloaking.so
   8 Server notice mask +F (far connects) is provided by contrib/sno_farconnect.so
   9 Information on the caller ID system can be found in doc/features/modeg.txt