How is publishing under a random pseudonym authorized?
Editor ultimately decides whether your pseudonym is acceptable or whether any pseudonym is acceptable for the journal. But you have to be practical about the decision to use pseudonym. If some professor, even respectable and famous one, writes you a letter saying


  "this person published a paper titled so-and-so under a pen name
  called ""."


would this really be convincing to everyone? Would this letter be written in ink on paper? What would you do with the paper letter in the XXI century? Scan and send .jpg's? Or attach it to a CV .pdf, which probably has 2-3 page limit? If it was in a digital form it must come from the professor's academic e-mail to have any credibility. Would he be willing to do that every time you need to prove it is you who wrote the paper? 10, 20, 30 years from now?