I can see Banned Users tab in one of the groups I'm in (screenshot), even tho I don't have permissions for banning people (Manage Group Bans), or any other admin roles/perms, I'm just a regular Member.
The banned users list and trying to ban someone requests return 403 Forbidden:
{message: "You don't have permission․", status_code: 403}
Here are my permissions from the /api/1/groups/grp_680d2e7e-e34f-41cb-a424-cb3a074f5216 endpoint
myMember -> permissions:
"group-instance-join"
"group-instance-plus-portal"
"group-members-manage"
"group-members-viewall"
I believe that the Banned Users tab displays incorrectly presumably because of the "group-members-manage" permission, and it should instead show if you have "Manage Group Bans" permission.