Closed Community: If a secondary journal has no entries, you can convert it to a closed community and then grant posting access to your primary account. After conversion, you can use your primary account to post directly to the closed community, but can no longer use the new community's username to post entries or comments.
Both those links are to FAQ 79 - should the "convert it to a closed community" point to FAQ 78 instead, since it describes how to convert a journal to a community?