Review: Improve comments

crates/matrix-sdk-crypto/src/identities/manager.rs

@@ -1965,7 +1965,7 @@ pub(crate) mod tests {
  assert!(!first_device.is_cross_signed_by_owner(&identity));
 
  let remember_previous_identity = other_identity.clone();
- // We receive a new keys update for that user, with no identity anymore
+ // We receive updated keys for that user, with no identity anymore.
  // Notice that there is no server API to delete identity, but we want to test
  // here that a home server cannot clear the identity and serve a new one
  // after that would get automatically approved.

crates/matrix-sdk-crypto/src/identities/user.rs

@@ -606,7 +606,10 @@ impl ReadOnlyUserIdentity {
  ) -> Result<bool, SignatureError> {
  master_key.verify_subkey(&self_signing_key)?;
 
- // The pin is maintained.
+ // We update the identity with the new master and self signing key, but we keep
+ // the previous pinned master key.
+ // This identity will have a pin violation until the new master key is pinned
+ // (see [`has_pin_violation`]).
  let pinned_master_key = self.pinned_master_key.read().unwrap().clone();
 
  let new = Self {