Merge pull request #27176 from peppy/document-classic-mod-no-rank

Add inline documentation as to why classic mod is not ranked

osu.Game/Rulesets/Mods/ModClassic.cs

@@ -19,5 +19,16 @@ public abstract class ModClassic : Mod
         public override LocalisableString Description => "Feeling nostalgic?";
 
         public override ModType Type => ModType.Conversion;
+
+        /// <summary>
+        /// Classic mods are not to be ranked yet due to compatibility and multiplier concerns.
+        /// Right now classic mods are considered, for leaderboard purposes, to be equal as scores set on osu-stable.
+        /// But this is not the case.
+        ///
+        /// Some examples for things to resolve before even considering this:
+        ///  - Hit windows differ (https://github.com/ppy/osu/issues/11311).
+        ///  - Sliders always gives combo for slider end, even on miss (https://github.com/ppy/osu/issues/11769).
+        /// </summary>
+        public sealed override bool Ranked => false;
     }
 }