In what way does it appear that you are right?
I assume the field you're talking about is either "comment" or "comment-to"? Those are fields for arbitrary strings that you can associate with your own transactions/recipients. The data is stored in your wallet, nowhere else.
The page you linked has nothing to do with bitcoind. Yes, you can store arbitrary data in the block chain, but only because there's no way to tell the difference between a public key hash and arbitrary data. It would be a dumb way to send out spam, because people would have to go out of their way to look for it, it wouldn't show up in their client in any way. You would, however, only need to encode it into the block chain once, not once per recipient.
