The assumption is that all involved heard/read what was said (as would usually be the case on small Usenet newsgroups), all agreed upon it enough not to object, and no one had any objections, so the statement is presumed to have been heard and acknowledged.
Guy: "Revenge of the Sith was the worst movie ever."
Group: "..." <-- usenet nod
Guy: "No one liked it? Good."
The occult art of changing the meaning of things by writing or stamping things on pieces of paper and moving them around. A skilled papermaster might give himself the privilege to drive, or make himself a citizen of many nations. Regrettably, most budding papermasters sell their souls and become file clerks instead.
I worked a bit of papercraft, and now I can drink legally!