Having finally experienced the LW author moderation system firsthand by being banned from an author's posts, I want to make two arguments against it that may have been overlooked: the heavy psychological cost inflicted on a commenter like me, and a structural reason why the site admins are likely to underweight this harm and its downstream consequences.

(Edit: To prevent a possible misunderstanding, this is not meant to be a complaint about Tsvi, but about the LW system. I understand that he was just doing what he thought the LW system expected him to do. I'm actually kind of grateful to Tsvi to let me understand viscerally what it feels like to be in this situation.)

First, the experience of being moderated by an opponent in a debate inflicts at least the following negative feelings:

1. Unfairness. The author is not a neutral arbiter; they are a participant in the conflict. Their decision to moderate is inherently tied to their desire to defend their argument and protect their ego and status. In a fundamentally symmetric disagreement, the system places you at a profound disadvantage for reasons having nothing to do with the immediate situation. To a first approximation, they are as likely as you to be biased, so why do they get to be the judge?
2. Confusion. Consider the commenters who are also authors and manage their own threads through engagement, patience, tolerance, and a healthy dose of self-doubt. They rarely feel a need or desire to go beyond argumentation and voting (edit: at least on a platform like LW with mods pre-filtering users for suitability), so when they are deleted or banned, it creates a sense of bewilderment as to what they could have possibly done to deserve it.
3. Alienation. The feeling of being powerless to change the system, because so few people are like you, even in a community of people closest to you on Earth in ways of thinking. That you’re on an alien planet, or a mistake theorist surrounded by conflict theorists, with disengagement and self-imposed exile as the only ways out.

Second, this cost and its consequences are perhaps systematically underestimated because the admins are structurally immune to it. An author would almost never ban an admin, meaning they never (or rarely, perhaps on other platforms) experience these feelings. They, being authors themselves, see the author's pain firsthand, but the commenter's feelings are merely an abstract report at most. This seems like a source of bias that becomes obvious once pointed out, but doesn’t appear to have been made explicit before, at least as far as I’ve seen.

I don't want to relitigate the policy in a balanced way at this point, but simply to introduce some potentially new considerations. So, admins, no need to respond now, but please keep these points in mind if you do decide to rethink the policy at some point.