I agree with you. Maybe change the comment
/* UID and GID are separated by a dot and UID exists. */
to say a bit more on the matter, to prevent a zealot from arriving 2-3
years from now and proposing removal. Just a few words to hint . support
will stay forever.
It seems the sentences in the man page could be changed a bit. Rather
than speaking about Previous versions, it could say POSIX (rev?)
deprecated '.' and introduced ':' as the default seperator, however '.'
seperator support remains for widely required backwards compat. The current
sentences speak a bit too strongly about '.' actually being gone.
