What matters is how public perceives this, too. Posting corp stuff on the org domain/site means that then they are fully corporate-like. Which maybe is simply the case.
You can't justify that its not the case because Mofo owns Moco.. then say both Moco and Mofo share everything without implying its all just a corp. (or the opposite, but not both).
If I'm understanding you correctly, you're saying that the tone of this post is too corporate for a .org and is a bad choice if we want to imply that Mozilla isn't just some for-profit company (which we don't, we like talking about how we're non-profit and open source and mission-driven).
Honestly I don't think anyone cares. We'd get the same trouble for posting corporate speak on a .com vs a .org because by the time you care about that, you already know enough about Mozilla to be bothered regardless of the domain.
Phrases like those belong in press releases, not a blog post from an organization intelligent people respect.
I mean it's sort've a redundant term, but in context (positive growth of Firefox users, something that has been falling for a while now) it makes perfect sense to me. What did you think he was saying?
The corporation is a wholly-owned subsidiary of the non-profit, so the .org domain isn't necessarily a misrepresentation, either.