So I called the nice people at Hershey's today, because I couldn't get any clear answer on the internet as to whether Reese's Sugar Free Peanut Butter Cups had gluten in 'em or not. The helpful lady, whose name was Maria, told me that the ingredient list will always mention if a particular ingredient is sourced from wheat, or soy, or one of the other things people are commonly sensitive to -- ie, you don't have to worry that the cellulose or polydextrose or some such actually came from wheat, and has gluten. If it doesn't say wheat, it ain't. She said that they also do their best to avoid cross-contamination between products.
I suppose it's not impossible that a few molecules of gluten wind up somewhere they're not supposed to be. But the actual recipe for the Reese's Sugar Free Peanut Butter Cups does not include any gluten. Nor does the recipe for Hershey's Sugar Free Special Dark, which I also have long kept on hand. I'm going with the idea that these are okay -- in moderation, which is how I've long eaten them anyway.
These candies still contain sugar alcohols, of course, and will, in quantity, make you socially offensive. Indeed, I think it's possible that some folks with gluten-triggered bowel problems have had gut issues from the sugar alcohols, and assumed they'd gotten a little gluten instead. My point being that these may be sugar free, but they're still candy, and that means that they're a fringe food, not a staple.
But it makes me very happy to not feel like I need to give them up entirely.