As to the specific questions.
No, I am not particularly enamoured with anal sex and never require it. That said, I'm very much into it right now because my girl gifted me sole use of her ass. And that appealed to me. Especially as when I take that gift her reaction is unique. She says she feels extremely submissive and used when I take her. And I must admit, it is not only quite heady... but just a little addictive.Yes, I think if it (or any body) is not a limit, then it belongs to the dominant to use as he sees fit*and should subs submit even if it does not exactly thill them afterall it is a part of being submissive .As I said above, my opinion is never... unless the dominant detests it himself and would never take pleasure from the act of punishing... but that's just me.should it be used for punishmnent ?
* ~'as he sees fit' presuming that is the nature of your D/s relationship. I can imagine different kinds of D/s where there is more "control" retained by the submissive.