You can submit a post to All after checking Exclude From All. The post is never shown to anyone but maintains its presence in the history of your posts. This allows the creation of "phantom" posts that need a direct link.
I suppose it can be treated as a feature instead of a bug.
It would be great a user could have the Share Link and Discuss buttons automatically set the subverse you are posting to the one you used the buttons in. EX. Using the share link button in the Books subverse will send the link you are about to post to the Books subverse unless you change it.
There doesn't seem to be anything here yet