If you've got time to dream up ways to be witty in order to be snarky to a co-worker, then you've got too much time on your hands at work and clearly need to fill it with other responsibilities.
I would hazard a guess that this letter was to a hypothetical employee, rather than for a real situation. And its purpose was to illustrate the type of code review new employees can expect and are expected to give, in a whimsical way. I quite liked it.
That's right! Get back to work. That's all you're good for, after all. Just keep working! Have a funny thought you want to jot down? Sorry pal forget it you clearly should be working, endlessly, tirelessly. Don't forget you're here forever. Working.