message: Add clarifying comments.
diff: @@ -228,17 +228,22 @@ where
  )
  }
  Event::IsBonded(Some(mut known_signatures), fs, true) => {
  + // New finality signature from a bonded validator.
  known_signatures.insert_proof(fs.public_key, fs.signature);
  // Cache the results in case we receive the same finality signature before we
  // manage to store it in the database.
  self.linear_chain_state
  .cache_signatures(*known_signatures.clone());
  debug!(hash=%known_signatures.block_hash, "storing finality signatures");
  + // Announce new finality signatures for other components to pick up.
  let mut effects = effect_builder
  .announce_finality_signature(fs.clone())
  .ignore();
  - // If new, gossip and store.
  if let Some(signature) = self.linear_chain_state.remove_from_pending_fs(&*fs) {
  + // This shouldn't return `None` as we added the `fs` to the pending collection
  + // when we received it. If it _is_ `None` then a concurrent
  + // flow must have already removed it. If it's a signature
  + // created by this node, gossip it.
  if signature.is_local() {
  let message = Message::FinalitySignature(fs.clone());
  effects.extend(effect_builder.broadcast_message(message).ignore());
  