Update comments

osu.Game/Online/Multiplayer/MultiplayerRoomSettings.cs

@@ -36,9 +36,6 @@ namespace osu.Game.Online.Multiplayer
         [Key(5)]
         public IEnumerable<APIMod> AllowedMods { get; set; } = Enumerable.Empty<APIMod>();
 
-        /// <summary>
-        /// Only used for client-side mutation.
-        /// </summary>
         [Key(6)]
         public long PlaylistItemId { get; set; }
 

osu.Game/Online/Rooms/Room.cs

@@ -149,8 +149,8 @@ namespace osu.Game.Online.Rooms
                 Status.Value = new RoomStatusEnded();
 
             // Todo: This is not the best way/place to do this, but the intention is to display all playlist items when the room has ended,
-            // and display only the non-expired playlist items while the room is still active.
-            // In order to achieve this, all expired items are removed from the source Room.
+            // and display only the non-expired playlist items while the room is still active. In order to achieve this, all expired items are removed from the source Room.
+            // More refactoring is required before this can be done locally instead - DrawableRoomPlaylist is currently directly bound to the playlist to display items in the room.
             if (!(Status.Value is RoomStatusEnded))
                 other.Playlist.RemoveAll(i => i.Expired);
 

osu.Game/Screens/OnlinePlay/Multiplayer/Match/BeatmapSelectionControl.cs

@@ -77,6 +77,8 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Match
         private void updateBeatmap()
         {
             Debug.Assert(SelectedItem != null);
+
+            // When the selected item is null, the match hasn't yet been created. Use the playlist directly, which is mutated by song selection.
             PlaylistItem item = SelectedItem.Value ?? Playlist.FirstOrDefault();
 
             if (item == null)