Even though I got
banned suspended, I'm able to mark a question as a favorite. Is this functionally correct?
If by ban, you mean that stackoverflow isn't accepting questions/answers from your account, then, why would it be appropriate to prevent you from marking questions as favourites?
The ban is to prevent negative behaviour that detracts from the value of the site, i.e. poor questions/answers. You being able to mark a question as a favourite doesn't, and I'd be hard presssed to see how it could, detract from the value of the site (unless you sit and mark, lets say, all the questions, as favourites).
A fix will be deployed in the next push.