Even if he's just trolling and this is a persona he's putting on, it isn't funny. Huge HP.
I unfortunately think he was trolling when he claimed to be a left-winger, but is dead serious about his views now. I don't know of any troll who would be dedicated enough to make over 10,000 posts on a white supremacist forum over the span of years just as an act. the only way I could see him being a troll is if he's lying about that Stormfront account being him, but it's been all but confirmed that it is him, since he had his account name from there as his display name on here back in Sept. 2018, as Virginia noted. the only reasonable conclusion is that he's exactly what he appears to be, an individual with thoroughly despicable white supremacist views.
The Stormfront poster in question has been quoted in mainstream news articles stretching back to 2012, so this is someone who was definitely known at the time that Matthew27 pulled that stunt. I don't think him having connected himself to this person in September 2018 necessarily refutes the idea that it is a lie, but ultimately it is an unimportant question. Either way he should be banned.