Hope this helps.
This transaction is embedding a message inside of a non-standard output script, which shouldn't be possible.
It is restricted by the standard Bitcoin client implementation. Neither the transaction scripting language[0] nor the transaction[1] restricts it, so you would need to do it yourself or write a custom client to embed a message.
http://garzikrants.blogspot.com/2013/04/on-bitcoin-data-spam...
Bitcoin is a really amazing piece of software and algorithm engineering. It is highly unlikely, although not impossible, that it was designed by a single individual. The scale, relatively bullet-proof crypto design (most systems are rigorously peer reviewed and still break), and the massive potential impact on global finance all point to a nation-state as the designer.
PG actually launched a thread with the same conclusion, and it seems eminently plausible to me.
As an example, JK Rowling released a book under a pseudonym. Very few people knew it was written by her, but one of those (a solicitor/lawyer) let slip to a friend, who then tweeted a tip to a journalist. It took a matter of weeks from publication for her to be outed. We are 4 years into bitcoin and there has not been anyything like this to suggest a large group worked on it.
If anything the lomger it goes the more likely it is that Satoshi Nakamoto was acting alone. Aditionally if there was a group of people then many of those would have had access to the numerous coins that were suposedly generated by SN during 2009. Surely some, one, any of those would have tried to access a portion of the coins to liquidate them.
Givent hat neither of these have happened it is more likely that a single individual was responsible and he/she is very strict with regard to their secuirty. i.e. they knwo that using any of those coins increases the chance that they will be tracked down. Whereas if it was a team then any one member may feel they could get away with it. Operational Security gets easier the fewer people that know about it.
the day before that leak you could have used exactly the same argument against the existence of a comprehensive NSA surveillance program ... someone would have leaked it already, right?