HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

Even so, it doesn't really affect the gameplay.
HD+ does affect it, but you can only play against other HD+ players.

Well, that's obvious, password-protected saves will still win the argument between HD and HD+, but it's interesting what prompted this change with level 2. Maybe they should have at least polled the community to see if they even wanted this.