From a quick read of the Reddit post and comments, people there seem pretty divided on whether this is legitimate. One person claimed that it's pretty well accepted in Spain that Columbus is Pedro Madruga but it's not accepted in other places because of the translation issues. Another person claimed that there is ample evidence that Columbus has a documented past and is not Pedro Madruga. flagamuffin, do you have any insight on which side is more widely accepted by the historians?
Also everyone but Shakespeare was Shakespeare. Amusingly, authorship identification is a thing in computational linguistics because of that question, so you have English professors' conspiracy theories to thank for Big Brother being able to figure out who you are from your hubski posts.
On The Media did a whole hour recently about where Shakespeare conspiracy theorists come from and why they continue to exist. Worth a listen if you have some time.