The point of wikichip is to document all the existing identifiers, the removed ones and the deprecated ones, some command and identifier are not documented on purpose in the help file, while some are just undocumented.
/finger is an old things which I believe was removed, (some command support switch which means 'use the finger window'), this shouldn't be documented in the help file.
Wikichip is not missing the commands you listed, there aren't mIRC commands, they are IRC server command, for instance /nickserv is not even a thing, only IRC dealing with nickserv may have this command, it's not even mandatory.


Looking for a good help channel about mIRC? Check #mircscripting @ irc.swiftirc.net