Hi! @PitaJ thank you for the quick reply.
I understand that an absolute URL have the protocol, but most of the normal users, at least in our forums, don't know what that is, some use it just because the copied from the browser, but sometimes a user doesn't add it, and having that links as relative URL returns a 404, causing a bad experience.
Some CMS have a sanity check like Django and WordPress if you add a link inside a WordPress, they check if it's another domain and adds the protocol, so the user doesn't have to add it.
I think it's a good measure to prevent bad user experience.