Helpful tip: if, hypothetically, you come across a prolific poster who seems to only thrive on bitter negativity, you can go to their profile and click the "block" option next to the "follow" one near the top of the page and they'll never turn up in your browsing again. Good for peace of mind.
The user Mutant seem to be going around various communities to either vent their misplaced rage or cause shit. Or maybe both. Check out their comment history. Then feel free to block them.