I'm not stupid! I swear!
"[...] this moisturizing lotion contains SPF 30."
Anyway, I got a note back saying, "SPF is not an ingredient in the lotion, so you shouldn't use the word 'contain'," followed by a link to a Yahoo Answers question about "what is SPF" or something.
Now on one hand, they're absolutely right. When you really think about it, "contains SPF" is a silly thing to say, so I changed the phrasing a bit. On the other hand, people do use the phrase "contains SPF", right? I'm not just hallucinating, right? Because it made me really paranoid. It sounds perfectly natural to me. Sure, it's not completely logical, but I would say that "contains SPF", "has SPF", or "with SPF" are all generally accepted phrases for the general concept.
Also, the Yahoo Answer link kinda pissed me off. Like, I know what the hell SPF is. I don't think that sunscreen contains SPF particles or whatever. I don't know. This was one of those situations where the change was perfectly acceptable, so I did it since there was no real reason to argue against it, but at the same time, I just want people to realize that I wasn't being incompetent, either. People say "contains SPF"! I swear!