Tagging of user generated content (UGC) is the means by which community members can help other members search for content.
Typically, tags are applied by authors and administrators in the author environment. Tagging UGC is unique in that UGC tags are applied by community members in the publish envronment.
The tag namespaces and taxonomies are the same for both applications.
The default permissions are set to not allow tag namespaces to be read by everyone in the publish environment.
Because tags are applied to UGC in the publish environment, read permission needs to be enabled for community members in order for them to be able to select tags to apply.
The following is how it appears in CRXDE when an administrator applies read permissions to /etc/tag/discussions for the group Community Engage Members.