Ahhhh... declaring the game.
You should really read "Why is that So Funny?" by John Wright.
He sees a clown performance (actually all theater making) like a big game. Some times the game is "declared" and sometimes not. When Laurence Olivier played Hamlet at the Royal Theater for the Queen, he did not declare the game though he was definitly playing one. When the group that did a production of "Hamlet" in a Bouncy Air Castle, jumped around Elsinor air castle, they did declare the game.
Clowns automatically just by putting on the makeup and nose, declare the game. By doing it we say "I know this is silly, and so do you, but just go with it. Play along." and the audience does cause it is much more fun that way.
The whys of clown makeup are both pratical and traditional. My personal hypothosis of the origion of the traditional clown face is that it was a parody of the drunk. The cheeks, nose and mouth are flushed red with the rest of the face looking rather pale. It was kept around because it attracts attention and is easy to see and read from a far way away. The baggy, colorful, and often mismatched clothes are also easy to see, and also can be funny simply becuse they are wrong, (wrong size, wrong color, wrong style and so on) but the clown doesn't think so. If he went around knowing it was all wrong, it would break the rules of the game, then it wouldn't be funny.
You really should find that article. There are many intellectually inclined clowns here who are always looking to discuss (or tear into as you found out
) stuff like this, and it helps to have primary scources.