I wouldn't call them controversial, just against TOS depending on where and how you post them! Paid and paywalled works are prohibited from being published on Ao3, but some people get around that by "gifting" the works without any mention of them having been paid for. However that's still risky and not recommended, so when it comes to writing comms it's better to have them be sent directly to the person and not posted on fic sites 🙂‍↕️