I'd argue there's a vast difference between using two different, accepted spellings of a word, and using a Chrome extension that alters English words, transforming them into not English words.
I think you might have misunderstood what cutspel is trying to achieve. This is the same thing as what NYT did by choosing a different spelling - that is to reform English spelling through familiarity with a new spelling. It worked for theater so why not other words.
The text on the page after modification by cutspel is still English - just more rationaly spelt.
