>>1
The easiest solution would be to use the existing framework:
prague itself.
Just start making posts in base64. Add a header which explains that the following is base64-encoded, but do not provide anyone with an adapter which decodes valid messages and filters out the rest of the shit.
Those who can code and thus have a chance to participate in a meaningful programming discussion would be able to implement the software on their own.
As soon as the plebs somehow get their hands on a copy of the program, we just change the encoding algorithm to something more involved.