Poll. So, what exactly is Hit&Run?

...if not, then it's your own fault – you didn't position yourself correctly, you didn't separate a single unit, etc...

That's a good argument. Then all this discussion about banning Hit&Run tactics isn't worth the trouble; it's your own fault: you positioned yourself incorrectly on the map, giving the opponent the opportunity to use this tactic.

If we're talking about Warlords, then in early encounters, Hypnosis is often much more effective than direct damage spells.

Separately, I'll explain my position: an expert Berserker cannot be considered a Hit&Run tactic at all. Because in the classic formulation, Hit&Run implies - attack and retreat, both when using direct damage spells and with so-called "power Hit&Run" (mass haste), for example. ...

You can play with words, or you can think about the meaning. Why is magical Hit&Run banned, but power Hit&Run isn't? Because with magic, you can inflict significant damage to the enemy's army without significant cost (1500 to buy back the hero on an Angel, let alone Firebirds, Greater Serpents, etc., and 2500 to buy him back from the tavern later), while power Hit&Run requires a powerful attacking stack with the first move and, therefore, a lot of money to buy back units.
Attacking with a Berserker and then buying him back is closer to the first case and will cost, at worst, 1500 more.