In certain posts Satoshi uses British style spelling (ie, “optimisation”) but in others, he chooses American style (ie, “criticized”).
 
au.linkedin.com/in/agulhati
The Indian educational system follows British spellings (being a former British colony) Ashish pursued his bachelors degree in english in India, Delhi Vishwavidyalaya, B.A., English Literature (1993 – 1996).
He also studied in the US, Willamette University (1991 – 1992) and Swinburne University of Technology MIT, IT (2009 – 2010).

Such a person could use British and American English interchangeably without even knowing it.
Its should be a fairly common trait among Indians who have their education/work split between India and US.

My drop in this sea of speculation.

Edit:Being a non-native English speaker, I use British spellings everywhere except the internet, where at times depending on the forum and the audience i deliberately use American spellings, the internet has weird influences. Its a choice non-native English speakers enjoy. For a person with an educational background spanning both sides of the hemisphere, interchanging spellings and styles should be natural.


Indian Spelling: India's Apollo Tyres to buy US based Cooper Tire for $2.5 billion
http://www.reuters.com/article/2013/06/12/us-cooper-apollo-takeover-idUSBRE95B0H820130612