The user wasn't banned but rather had posting restrictions so could still access your community and perform all other functions except for posting. If you do not want someone accessing your community, you will need to suspend them from your community via a ban. This would either be meeting the warning points necessary by your warning configuration, if the moderator has permission to setup a custom warning solutions (i.e. suspend/ban them), or as an administrator, using the ban feature to suspend them on their ACP profile.