Fediverse

This is of a piece with "Mamdani isn't left wing enough for me" / "AOC supports genocide" / "Bernie is a Zionist" kind of glib one-liner reasons why left-wing people need to stop supporting left-wing things, because they're not really virtuous enough, and so we need to abandon them in pursuit of some kind of imaginary virtue solution instead of just having unity.

TL;DR: They took some funding from Marc Andreessen long ago, they were willing to give blogs to everyone including Nazis (bc free speech) and the whole internet yelled at them, so they caved and removed the Nazis. IDK how this particular push notification happened, but I would bet that the blog will be removed. They are not wholly ideologically pure, I think Richard Spenser is the worst person they willingly host and he's pretty bad, but they don't allow Nazis anymore specifically because of the hue and cry it raised up the first time.

More conversation about it here, I don't have the patience right now to write up a full explanation. TL;DR someone who's panicked at you about the Substack Nazi problem is listening to something that's mostly designed to hurt a mostly left-wing platform.