I disagree. It'll discourage leaders to use the public channels to discuss and plan as random newbies might get their messages and share it with their new realm.
I've yet to be in a realm that discusses anything of importance to the enemy in public. If you're not in an army, you'll pretty much have no idea what the realms military is doing in most realms. Most you tend to see is maybe some scoutings, a few arguments about something and maybe a diplomatic update from the ruler on something that every other ruler already knows. So I don't really see the harm in giving a glimpse at the past weeks messages.
Though this does raise the point that the game has become somewhat segregated. Most orders used to go realm wide, but the army system has made that disappear. This has very effectively shut out those that aren't in an army from easily following what's happening in the war their realm is fighting. Mostly that means courtiers etc. live in their own bubble while the army lives in its own.
For example, in Darka my priest character knows about the armies of the realm very little. All he hears is a few battle reports now and then. He has no idea where they're going, when they're coming home etc. He has no idea that within the army there have been some nice arguments that would have been fun to read. That information used to be very public. Now it would be an hassle to ask for updates all the time so you could live a little through the other nobles in the realm. He loses out on a lot.
That's probably also one point to consider in retention. If your character is not in the right segment of the realm, you just miss a lot of what happens. A lot of that being missed used to be in the realm wide channel.
