Lore wise the communication is of course encrypted or coded, plus you do detect that a pather cell is active on the planet. You just don't know where their physical support is coming from. Without a comm relay the people of your planet will have a hard time coordinating things with other systems, purchasing stuff, getting the news and such.
I was expecting these idiots to have their comms unencrypted because they hate tech...
But then again they hate tech so much that they only communicate in writing? like having a literal courier bring the message across on a piece of rock. yeah good luck detecting that with sensors.
I just wish Comms do more than just stability, I know, I prioritize stability. I always aim to have at least 13 stability in every colony so that if Ludds do anything, they can't do ***. And over 3K defense, good luck finding enough fuel for that with your jihad ships. but please can we "tune" in to them, rather than just listening to a general channel, we focus our sensors and computing power to find that one Pather who forgets to encrypt their connection, or a pirate.