Steps to recreate:
- Go to create a new Arts Proposal.
- Type in 'Star Trek'.
There's a handy duplicate checker, and it detects (at the time of writing) a Star Wars proposal. What it doesn't detect is Science Fiction and Fantasy, which is an actual duplicate, and I think can feasibly be detected.
I suggest that the duplicate checker be expanded to search tags of SE sites, and if it finds matches, it offers those sites as possible duplicates.