Category Ban is not supported but would it be possible with a plugin?

[Heliosurge (Dan DeMontmorency)]

@Crius

Category moderators cannot act on the Users themselves, only on the category, however they should, in my use case, be able to impede some users from participating if they break some of their sub-forum rules.

Have you considered using groups? Create category with 2 groups for access. 1 Group is your category Mods. the Other is your participants in the subforum. The participant group is required to request access to Subforum area. Your cat mods some or all are owners of that group. If a member breaks rules requiring to kick them from sub firum. Kick from participant group and communicate with other cat mods on duration.