Supporting capitalist spaces when anarchist alternatives exist is supporting capitalism. As anarchists, we shouldn't be propping up an awful corporation that has allowed stuff like r/cutefemalecorpses, r/publichealthwatch, r/altright, r/fascism, r/fatpeoplehate, r/the_donald, r/incels, r/coontown and r/jailbait to prosper for years.
Especially when maintaining a sanitized, controlled-opposition 'anarchist' sub on reddit ensures the actual anarchist alternatives like raddle and 0chan will stagnate without a mass migration. Ensures that anarchism will be dilluted and liberalized for a generation of people that think r/anarchism is a representation of what we stand for.
Comrades that cling to reddit are harming the movement. Reddit is a reactionary safe space and it harms people. Kills people.
If the community there really give a shit about anarchism, they would close the sub and have it display a message of protest over reddit's targetting of anti-fascists, and links to better sites that don't forbid anarchists from organizing against fascism or sharing anarchist literature.
It can also link to r/Anarchy101 so newcomers can still get radicalized. Make that the new primary anarchist sub on reddit, so people get started there, and move on to a real anarchist space once they pick up the basics.
Doing something like this would likely get media coverage. Would get new people interested in anarchism when they see we're sticking it to reddit and boycotting it for propping up reactionaries that incite violence against minorities.