Replies a post's author approves (FEP-5624), checked live with PeerTube

PeerTube puts canReply on a video whose comments wait for approval, and answers each comment with ApproveReply. A
persona's reply to such a post now waits (privapub.approval: pending), its Create going to the author alone; the
author's ApproveReply, signed by the author and naming the post answered, lets it out to its audience with
replyApproval, and RejectReply leaves it ours. A null canReply (PeerTube's open comments) says nothing; an empty one
refuses. The PeerTube scenario holds a comment for review and approves it through PeerTube's API (28 checks).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

FEDERATION.md

@@ -96,6 +96,8 @@ covered by unit tests written in their documents' shape.
   passed on by the owner (on its FEP-8b32 proof, or as its origin has it)
 - [FEP-8fcf: Followers collection synchronization across servers](https://codeberg.org/fediverse/fep/src/branch/main/fep/8fcf/fep-8fcf.md)
   (sent and honoured; see "Followers synchronisation")
+- [FEP-5624: Per-object reply control policies](https://codeberg.org/fediverse/fep/src/branch/main/fep/5624/fep-5624.md):
+  read (see "Replies its author approves")
 
 Planned (see `docs/ROADMAP.md`, phases P7 and P8, and the per-platform notes in `docs/INTEROP.md`): FEP-9098 (custom
 emoji), FEP-7888 and FEP-f228 (threads), FEP-7628 (Move), FEP-8967 (link
@@ -290,6 +292,12 @@ a post first met after its edits has them, and an edit that carries them brings
 - Our own posts state only `canQuote`: anyone may reply to, like and boost them.
 
 **Custom emoji** (`Emoji` tags) are read on posts, display names, bios and profile fields, at most 64 per object.
+**Replies its author approves** (FEP-5624's `canReply`, as PeerTube sets it on a video whose comments are moderated; a
+`null` one says nothing): a persona it names, or that the post mentions, may reply, and the reply waits
+(`privapub.approval: pending`), its `Create` going to the author alone. The author's `ApproveReply`, signed by the author
+and naming the post answered, lets it out to its audience with `replyApproval`; a `RejectReply` leaves it ours alone
+(`rejected`). An empty `canReply` refuses every reply (422).
+
 **Profiles** keep their header, profile fields, `manuallyApprovesFollowers`, `published`, `movedTo`, `indexable`,
 `memorial` and avatar and header descriptions. A post's title becomes `name` and is also the first, bold line of `content`, because Mastodon does not show
 `name`. A content warning without its own text uses the title, or "Content warning".