> Don't trust old-school typewriters and the postal system either. Letters are routinely opened and typewriters can be matched. For example, the Stasi (secret police of the former GDR - German "Democratic" Republic) had an archive of type samples of all sold models of typewriters for re-identification of political pamphlets.

That's theoretical. I highly doubt anyone extends that much effort to target typewriters anymore. The best they could probably do is match a series of messages to the same typewriter. Though they might not even be able to do that, because the law-enforcement skills to match typewriter documents to each other have also probably nearly completely atrophied.

You're probably more likely to be caught by being the weirdo still buying typewriter ribbons.