Currently, the ability to Delete a Collection seems to be hardcoded to System Admins only:
However, we have a Configuration in dspace.cfg which implies that Community Admins are given the ability to delete subelements by default:
#core.authorization.community-admin.delete-subelement = true
This dspace.cfg configuration defaults to "true", and yet it is ignored by the XMLUI in the Collection Edit aspect.
Community Administrators are able to delete Sub-Communities. So, it seems like the "EditCollectionMetadataForm" should be updated to the same settings as the "EditCommunityMetadataForm", specifically see this code:
This needs a volunteer, but is likely a tiny (possible one line) fix. PRs welcome.