I don't know if it can be called a bug or a feature request...
We host several domains, and each domain has its own dedicated IP address. We configured Postfix to use "Sender Dependent Transport Mapping" So the outgoing mail uses the domain's IP address and it works well. The problem comes when you (or any Internet mail server) connect to our mail server through the domain's dedicated ip address because the smtpd banner they get includes the server's hostname instead of the hosted domain name.
I think it can be called a "bug" because this issue is causing trouble with some servers tagging our emails as spam because the hostname in the banner doesn't match reverse IP address hostname or MX or SPF outgoing mail server name.
I can manually fix the issue editing /etc/postfix/master.cf and adding "-o myhostname=ourdomainname.com" to every domain we host, but I think it should be automatically added when Dependent transport mapping is in use or at least, be a configurable option.