[ansible]

If I had the free time, I'd create a cryptographic protocol running on top of telnet that looked like someone playing a MUD.

For email, you'd encrypt data to have it look like regular prose. So you'd only get a few bits per English word, but that would be sufficient for short messages. Could also make use of extra spaces in between words.

The real trick with that would be to take an existing document, and alter it to encode a message. So you'd be doing things like using synonym choice to get your bits.

[metalliqaz]

There aren't enough MUD players to make it inconspicuous.

[nualartlee]

Cat pictures and steganography.

[pferde]

Wait, isn't reddit already used for this extensively? With each subreddit being a separate comms channel. Or is there another reason why very little reddit content makes sense?