You changed "metabolized" to "metabolised" on 19 March 2005.
Then on 6 April, you added "synthesised", after you had changed to metabolised a couple of weeks earlier.
And this week you changed "labeled" to "labelled". 
It was only the last one that was done specifically to make that change.  The others are the type of thing I might inadvertently do myself, in the opposite direction.  Especially when I'm only editing one section, I'm usually not going to go back and check to see what the rest of the article uses (which might not be consistent in any case).
But it was the last one, with your editorial comment just saying "spelling" as if the spelling were incorrect, which made me look into it in the first place.  That's why I made sure that I pointed out that I wasn't changing the spelling just because of my own spelling preferences.