I've always thought the post to 4chan literally telling people to brigade us, followed by accounts trickling in that use almost the exact same MO (some combination of extreme porn, gore, Nazi propaganda, anti-Indian, anti-Jew, anti-Black, anti-LGBT) and how closely they seem to watch for new federated instances with open registration (Lemmy.ml is on what we call "open federation", so there isn't actually a comprehensive list of who we federate with that they can check for changes. Only the list of instances we block are manually configured.), and how several of these accounts pop up in quick succession before it all goes dormant for a while, all that's pretty suspect. The average 4chan troll would have gotten bored ages ago, especially once it became more difficult, especially especially once they stopped getting attention for it. The fact that it's persisted for this long definitely seems to be someone with a pretty strong grudge against us. I suspect they do this whenever they're bored or angry as some messed up coping mechanism/revenge plot, which is why it's so intermittent. Specifically Lemmy.ml because that's where almost all of the trolling is targeted.

Is it Soferman? I have no idea, they're not the only user who left (or usually, was forced to leave) less than amicably. China Number One, the user posing as a pro-PRC socialist but actually just posting racist, Chinese-supremicist BS that no actual socialist or anyone in the Chinese government would agree with is another candidate. Though at the end of the day, it doesn't really matter because we don't know who they are IRL anyway.