I think he's asking how it got so obfuscated in the first place. Seemingly, the spammers could just pilot a standard up to date client with a bot, rather than try and figure out the protocol.
I'm sure it's more complicated than that however, like client side rate limiting or something.
I bet they would put the rate limit in the client, since they did that with the banned word list, but rate limiting would make more sense at the server. Maybe they did both.
Now you could fire up a new VM for each client or use a botnet to do your bidding. Oh, how the Internet has advanced.
I'm sure it's more complicated than that however, like client side rate limiting or something.