well you see that little button that's a red circle with a slash through it, click that and no more spam
I know the trick to use comms without energy cost, no I'm not going to say how it's done, and I plead the Fifth on any question regarding usage.
5E to send a message with the new block/delete/reply system doesn't entirely make sense. Yes you could spam a guy while offline, but then he clicks 'block', no more messages from that guy ever again.
On a side note, could we have an option somewhere to 'remove' a comm ban? During some wars, it gets to be a big flamefest, but then afterwords the legions might become closer to buddies, and its nice to be able to remove those blocks.