I've asked the same thing a few months ago , and this was the reply :
Modlog is two weeks.
Maybe when an user is banned I think it easy to theymos add under the "rank coins" a little word: "Banned" ,
What do you think ?
Why do you need to know when someone else is banned?
Well to answer BadBear , it's pretty simple , Sometimes we want to contact someone (a friend) on the forums and we see them banned ... we just don't bother our selfs , also to make deals , let's say someone is selling something and he got banned (he left his BTC adress on the thread and asked to send BTC then he send product) .. so we just don't send Bitcoin while he is banned etc ... a lot of things , it would be really useful to be honest
Both Banning date , Banning reason should be also available on the Profile if you ask me
PS : Note sure if we are able to use private message while we are banned or not . speaking Theoretically