NewPipe (or Tubular if you like the sponsor skipping that is also available in revanced) might be something for you? Although it might be too little bloat for you as you can only read comments and not comment yourself
With this reasoning, would you say everything that a computer does makes sense, because it always follows the implementation? Or am I missing something?
To answer the question: The professor assumes the email referred to 1900-1910 with "late 1900s". As this was normal 20 years ago (and still gets used). He then gets upset realising the age difference between him and his student was likely the main contributor to this incorrect assumption.
Or the biggest finger