But thats your argument: It's an exploitable combat mechanic that hurts no one and we have the free option to not use it.
So it's not a problem according to your logic concerning flee.
Not the same thing at all....you should be able to flee. If you are fast and stealthy and can hit and teleport then yeah....that works wonders and it should. It's a tactic.....one that requires the player to think and be clever....these are the things that the game has to reward big. As long as the enemy doesn't see you and you can run circles around them it's fine.....a perfect way to go about building a glass cannon build...something that was simply impossible in DOS. Stealth and glass cannon builds and all these things are things that should work.
Now you're adding qualifiers:
Requires players to think and be clever
Shouldnt let you run circles around enemies
These are the same qualifiers everyone is concerned with. Flee is overpowered. It requires no thought to use and lets you circle enemies through said use. No one said remove it.
Just as you said the game is/needs to be modified so stealth =/= immortality. Flee should not equal instant win through picking off enemies one by one; that's not a tactic. That's like saying "well, if you shoot the barrel in the corner at each encounter it'll kill at least one enemy, heal you, let you restock all consumables, and stun all the enemies for a turn, and re spawn so you can do it again." <- That's bad.