Document the safe reward notifier requirements in UniStaker comments

src/UniStaker.sol

@@ -550,9 +550,19 @@ contract UniStaker is INotifiableRewardReceiver, Multicall, EIP712, Nonces {
   }
 
   /// @notice Called by an authorized rewards notifier to alert the staking contract that a new
-  /// reward has been transferred to it. Note the reward must already have been transferred to this
-  /// staking contract before the rewards notifier calls this method.
+  /// reward has been transferred to it. It is assumed that the reward has already been
+  /// transferred to this staking contract before the rewards notifier calls this method.
   /// @param _amount Quantity of reward tokens the staking contract is being notified of.
+  /// @dev It is critical that only well behaved contracts are approved by the admin to call this
+  /// method, for two reasons.
+  ///
+  /// 1. A misbehaving contract could grief stakers by frequently notifying of tiny rewards,
+  ///    continuously stretching out the time duration over which real rewards are distributed.
+  ///    It is required that reward notifiers supply reasonable rewards at reasonable intervals.
+  //  2. A misbehaving contract could falsely notify the contract of rewards that were not actually
+  ///    distributed, creating a shortfall for those claiming their rewards after others. It is
+  ///    required that a notifier contract always transfers the `_amount` to this contract before
+  ///    calling this method.
   function notifyRewardAmount(uint256 _amount) external {
     if (!isRewardNotifier[msg.sender]) revert UniStaker__Unauthorized("not notifier", msg.sender);
 
@@ -571,6 +581,12 @@ contract UniStaker is INotifiableRewardReceiver, Multicall, EIP712, Nonces {
     lastCheckpointTime = block.timestamp;
 
     if ((scaledRewardRate / SCALE_FACTOR) == 0) revert UniStaker__InvalidRewardRate();
+
+    // This check cannot _guarantee_ sufficient rewards have been transferred to the contract,
+    // because it cannot isolate the unclaimed rewards owed to stakers left in the balance. While
+    // this check is useful for preventing degenerate cases, it is not sufficient. Therefore, it is
+    // critical that only safe reward notifier contracts are approved to call this method by the
+    // admin.
     if (
       (scaledRewardRate * REWARD_DURATION) > (REWARD_TOKEN.balanceOf(address(this)) * SCALE_FACTOR)
     ) revert UniStaker__InsufficientRewardBalance();