@phnt >From there they can subpoena the service and get your data that way
Which wouldn't matter much for a service which doesn't keep metadata for its users. Though I assume few exist right now. The most intelligence agencies can do then is take control of the box the service is run on and log the metadata for incoming posts themselves. But that definitely isn't insignificant
edit: a million and one edits, because my posts are unintelligible garbage written by a halfwit