There's a few others. The KPAM was completely conflict-free with MLs helping them set up, it existed at the wrong time and in the wrong place though, collapsing with the assassination of their leaders. Mao was very friendly with them but they were probably only able to exist because they had communists in control in the territory next door. As soon as the situation in the civil war changed and they didn't have the communists in the next door territory they got destroyed.

I think there's space for MLs and anarchists to coexist. I believe that as long as anarchists aren't presenting a threat to the ML nation then they have no reason to interfere with what the anarchists want to do next door. Living in the shadow of communists is probably the only way for any anarchist society to survive right now.

Anarchists would probably play a very significant role in the fading away of the communist state in a post-capitalist world, being the major advocators of it and leading by example in any of their own societies that they managed to set up and hold. I'm actually pretty sure that there would be a few that would immediately attempt to leap to this once capitalism is no longer a global threat.