Update comment

src/compiler/binder.ts

@@ -1465,6 +1465,7 @@ namespace ts {
             }
 
             // Declare the method/property
+            // It's acceptable for multiple prototype property assignments of the same identifier to occur
             declareSymbol(funcSymbol.members, funcSymbol, leftSideOfAssignment, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
         }