I would just like to figure out why we (myself included) are so obsessed with faux smoke rings in the first place.
Easy answer: Eye candy! The food experience is so visual! If you look at something, and it doesn't have eye-appeal, your brain immediately decides it will NOT taste good (even if it does). We have seen that gorgeous pink ring around smoked meat all of our lives, so when it's not there, our brains tell us it isn't really BBQ. Even though we know it doesn't change the taste, it just makes the presentation so much more appealing!
I'll be interested to see what you discover with the celery powder, Coolio! Although nitrites/nitrates are not "artificial," I understand your need to put your wife at ease. Many commercial producers use celery powder to "fool" the consumer that their product is "all natural," but the simple fact is that it's a marketing gimmick, nothing more. Nitrates are nitrates, no matter what form they're in!