You can check if a Fact had been posted by going to the celebrity’s page on Hollowverse.com.
You can use the Search Page of the main site to search for the celebrity and check if the Fact is already on their page.
An easier, but less reliable way to find duplicates, is the “Similar topic feature” that you’ll see when you make a post here.
When you make a post, you’ll see something like this
Review the list of similar topics to make sure you’re not posting a duplicate.