Let's say I've got two detachments: one chaos space marine and one chaos daemons (one is the ally / batttle brother of the other). Check my logic subsequent here:
Chaos Space Marines are able to use Chaos Daemons' icons.
Chaos Daemons can not use Chaos Space Marine icons.
Is that right!?? Because that is what the "rules as written" seem to imply unless I've missed something?