Actually, you had the right idea in the first place. That glossary was added to the American edition of the book (which also dropped the final chapter, thus completely changing the ending of the story), and Burgess did not approve of it. He wanted readers to pick up the slang as they went along.
(Speakers of Malay, and/or Burgess experts, will note that I’m being obnoxiously clever with the post subject.)
woot?
From the webpage mentioned in the Straight Dope column, http://www.wikipedia.org/wiki/Leet, «“w00t”, “w007”, or “^/007” is a common interjection, analogous to “Yeah!” or “Yippee!”»
|-|//|o|-|
1337 |-|411 /\/3\/3|2 |)13
1+ |-|4 |33(0//\3 |o4|2+ 0|o|-| //\0|)3|2// 94//\1//9 4//|) (0//|o||+3|2 |2314+3|) (|-|4+$
|33$1|03$
1+ +4|<3$ |o|-|4|2 +o0 10//9 +0 |)0 1// |o|-|||11
wh1ch 1z why m0zt p30p13 d0 1t h41f 4nd h41f ph0r 1337 wh3n 1n94m3
Translation
hmph
L33T shall never die
It has become part of modern gaming and computer related chats
besides
it takes far too long to do in full
which is why most people usually do only half and half for L33T when ingame
j00 n33d +0 ch3k +i5 0u+ 
http://www.frashii.com/romjul.swf
//Miqlo
Had he mentioned it, the CR editors would probably checked more carefully.
btw. I’m so proud. I’m 17, use the internet everyday for stuff, but had never heard of leet. I entirely agree with Cecil when he says “This is |-|0r535|-|17”.
<Re-reads article>
Oh no. Do you think Cecil will think I am a twerp now? 
…Bu7 17 uR3 #3|_|*.
Pre-1996, we called l337$p34|< “B1FF talk” or “B1FFspeak”. Maybe someone else is out there who was also online ages ago and can confirm.
B1FF (a fictional character based on annoying then-pre-teens fancying themselves uP0R#4X0r) “invented” L337, and it was mocked and derided. B1FF also had a bad habit of abusing punctuation!!!111
And yes, L337 was used even by “non-L337” people so we could say adult words in an otherwise overly-censored forum.
I’m sure it would horrify most L337 people to know that I’m closer to 40 than 20 and can still read their crap.
j00 ||0 |^|#47?
1 C4|| 7y|*3 1|| |337 2.
=/=|| 7#0 1 7#1|||< 17 (V)4|<3$ PP| $0u|||) |)u(V)|o.
|<3^/|_, #u#?
Bleah. That cost me at least three I.Q. points. Grrr.
Love,
Milla
Well, maybe not a twerp, maybe an innocent. Here’s the 03-May-1991 column where he lists the phrases “‘go do [it] in the ass,’ i.e., bugger off, fuck off, fuck you” and “shot at and missed and shit at and hit,” and dozens more that could be considered twice as offensive. Somewhere there is a column where he discusses the appearance of the word fuck in Disney movies.
Editors? He don’t need no stinking editors. OK, Little Ed, sure, but what does he do?