Thanks to a comment from Ben, I’ve come to learn the real identity of Peter the Painter. He was a latvian named Janis Zhaklis. Ian Bone has covered the story and has an audio interview with Philip Ruff, who traveled to Latvia numerous times to uncover the story. (You can also watch the interview on youtube).
And there’s also an interesting bit about the story of uncovering the truth from the kate sharpley library (pdf).
The short of it is that Peter the Painter was not a damned bolshevik, and he most certainly wasn’t the bolshevik responsible for the literal eradication of the anarchists in soviet russia. That’s a relief. We get to keep our folk hero.