I'm not sure we are talking about the same person. Jstark1809 was probably a anarchist or libertarian but I'm not sure he could be described as "leftist" in the way we use the term today. And I don't think a nym in a "undisclosed European location" had much influence on US politics. Except that he helped make gun control next to impossible all over the world with his R&D in 3d printing guns with ecm riffled barrels.
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https://www.recoilweb.com/jstark1809-tribute-the-patron-saint-of-3d-printed-guns-171086.html