IDK what you mean by “domain host” but the thing about cloudflare ('s most prominent service) is that it’s essentially a voluntary MITM between you and your clients. They see ALL traffic going between your server and your clients. This is not normal. Normally traffic between server and client is encrypted with HTTPS. By using cloudflare’s proxy your are adding a backdoor to that encryption. Your registrar cannot normally see this traffic. Your certificate authority cannot normally see this traffic without issuing a malicious cert. But cloudflare can. And, if they wanted to, they could even inject malware to deanonymize users, spy on journalists, steal data, etc. As a matter of fact, they already do, but instead of calling it “malware” they call it “analytics”, so it’s okay 👍