Plugin idea: "See also"

If a user canEdit() an entity, she could add one or more links to other entities, to be displayed above the comment form.

The form would take a URL. If the URL could be reliably matched to an entity, a "links_to" relationship would be formed. If not, it would require "see_also" multi-value metadata.

If order of the links are important, I'm not sure how to do that...