Have you ever tightened a free tier and realized you had no way to tell the people it affected?

We used to let people use the core function without an account at all. Turn up, get a result, leave. This week we put a free account in front of it. Same allowance, same features, no card but you sign up before you get anything. The reasons were boring and real: we couldn't attribute anything to anyone couldn't tell a returning person from a new one, and an anonymous endpoint that costs money per call was an abuse problem we'd have to solve eventually. What we didn't think through is what to say about it. The people affected are almost by definition people we can't contact. They never gave us an email. That was the whole point of the thing we removed. Every draft announcement reads either defensive or like we're dressing it up as a feature. How do you communicate a change that is genuinely worse for some users without it sounding like spin?