Features suggestions go in Contribute > Feature, but I can foresee that the reply will be something like “it’s not a good idea, there won’t be any official such feature or theme component” 
I agree with Jagster.
I think a public, permanent, full list of banned people probably wouldn’t bring good.
However, if you ban someone, you can create a topic or post, which explains publicly why this person was banned. This message would be for an informative purpose and a warning for other problematic users.
No need for a detailed list.
Asking users not to discuss the ban can also be done if you feel it.
Some forums do it. Usually, the message conveys: “It’s our forum, there are rules, we’ve given warning(s), they’ve not listened, no more to argue”.
Some forums are willing to discuss the matter, it’s your call. It depends on how you manage your forum, how serious is the issue, how the community behaves, and many other factors.