Sorry to interrupt this thread, but the Scrabble board is
separate medium. (IMHO)
A Scrabble board can be used to send a message. It does
place very strong restrictions on the message sent, but that
does not prevent it from being a medium.
Just the presence of a Scrabble board somewhere will send a
message. Not much of one, but something. If you further put
tiles on the board, then it becomes a substrate for another
medium and another message.
Elijah
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currently reading _Understanding Media_ by Marshall McLuhan