so you've got a person on a channel.
you issue the command:
/mode #channel -o+o person person
pircd happily deops, and then reops the person.
except that it tells everyone that what it did was:
*** Mode change +o-o person person by You.
mirc looks at that, and says "hey, that op'd person was
op'd again (which doesn't do anything) and then deop'd,
so now they're deop'd, and maintains that in its channel
state, in correctly.