I've seen some that fit what he's talking about. It's sort of hard to explain... you've got 4chan-ish derivative sort of people that seem to go either one of two ways. They either start identifying as Alt-Right, or they proclaim themselves the True Left. Their views actually aren't very different at the end of the day (both hate anyone they think will make them behave, like cops, landlords, and their parents), and both still have that sort of edgy thing where they don't have a lot of tolerance for the purely tumblr-ish sort and like to shitpost. About the only difference between the groups is that the True Left ones seem to only believe in shitposting For The Cause, they're more consumed by it, while the Alt-Right ones are pretty much blatantly using politics as an excuse to be trolls and they don't really care who knows it.Edgier in what way? Most Berniefags I've seen get offended incredibly easily at any sort of edgy shit.
Bernie Bros are the ones who came up with the "Biden buries dogs alive" meme, after all. It's a shitpost that they've wound up dedicated to and it's definitely that same sort of ridiculous nonsense that has some actual humor to it that you'd expect more out of someone who's not so touchy and easily offended. Mostly you can tell it's lefties doing it because they get mad when right-wingers try to join in the fun.