Document a little about moderators and tiers (#1909)

Note, partly writing this down to make sure everyone's in agreement with what's written.

Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

docs/project/moderators.md

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+# Moderators
+
+<!--
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+-->
+
+## Overview
+
+Moderation is primarily focused on Carbon's Discord and GitHub, but generally
+applies to the [collaboration systems](/CONTRIBUTING.md#collaboration-systems).
+Moderators are empowered to improve community discussion and enforce the
+[Code of Conduct](/CODE_OF_CONDUCT.md). Conduct decisions are ultimately the
+domain of the [Conduct team](/CODE_OF_CONDUCT.md#conduct-team), although
+moderators will often act in order to protect the community.
+
+All moderators will have the "moderator" role on Discord. Some moderators are
+_senior moderators_, and will have extra privileges to help address harmful
+conduct. Senior moderators will have the "senior-moderator" role on Discord.
+
+## Becoming a moderator
+
+TODO: Need to figure out right process for asking. (that is, how?)
+
+The Conduct team reviews new moderators. Community members will be considered
+mainly based on their history in Carbon Language community spaces (Discord,
+GitHub, etc.), although applicants may also note history in other communities.
+
+Prior to being granted moderation privileges, new moderators will need to attend
+a workshop in order to help orient them with the Carbon Language community's
+values and moderator expectations.
+
+## Promotion to senior moderator
+
+The Conduct team reviews promotions to senior moderator. Moderators will be
+considered for promotion to senior moderators when:
+
+-   They have demonstrated that they will be active moderators.
+-   They are making decisions consistent with the
+    [Code of Conduct](/CODE_OF_CONDUCT.md).
+-   Senior moderators are taking actions which require senior moderator
+    privileges at the moderator's request.
+
+## Moderation powers
+
+There is a moderation playbook for moderators with instructions on how to use
+these powers. This enumerates specific actions a moderator may take.
+
+-   **Discord**
+
+    -   **Timeout user** (all): Prevent a user from sending messages on the
+        Discord server for up to a week.
+
+    -   **Delete message** (senior): Delete a message owned by another user.
+
+    -   **Kick user** (senior): Temporarily remove a user from the Discord
+        server. Note that users can rejoin the server, and so banning is
+        typically preferred.
+
+    -   **Ban user** (senior): Permanently remove a user from the Discord
+        server.
+
+    -   **Slow-mode** (senior): Limit the rate of discussion on a channel.
+
+        -   Slow-mode is tied to the ability to generically edit channels.
+            Moderators are generally expected to use the channel edit power
+            judiciously, preferring to leave channel edits for admins.
+
+-   **GitHub**
+
+    -   **Convert issue to discussion** (all): Moves an issue to a discussion.
+        This is mainly organizational.
+
+    -   **Hide message** (all): Collapses a message so that its text is not
+        immediately visible, reducing distractions. Recommended for moderators
+        when a particular message is unproductive. Users can still view the
+        original content.
+
+        -   This cannot be done with the first message in a conversation.
+
+    -   **Lock conversation** (senior): Prevent more discussion on a topic.
+
+    -   **Edit message** (senior): Edits content of a message. Users can still
+        view the original content.
+
+    -   **Edit title** (senior): Edits the title of a thread.
+
+    -   **Delete message** (senior): Removes a single message from a
+        conversation. Hiding or editing messages is preferred.
+
+        -   This cannot be done to the first message in a conversation.
+
+    -   **Delete conversation** (senior): Deletes a full GitHub conversation.
+        Hiding or editing messages is preferred.
+
+    -   **Block user** (senior): Blocks a user from all repositories.
+
+    -   Note: We use custom roles which have
+        [limited access options](https://docs.github.com/en/enterprise-cloud@latest/organizations/managing-peoples-access-to-your-organization-with-roles/managing-custom-repository-roles-for-an-organization)
+        versus what
+        [base permissions](https://docs.github.com/en/organizations/managing-access-to-your-organizations-repositories/repository-roles-for-an-organization)
+        allow.
+
+-   **Google Docs**
+
+    -   There are limited powers for moderators on Google Docs, but access to
+        Google Docs is already restricted. At present, the right action is to
+        respond or comment on an issue as needed, and report to the Conduct team
+        if further steps are necessary.