Wait, so you're saying that a majority of players can override any other player's entire RAM? That sounds like an amazing paradise for hackers and griefers :D
Well in the case of my game engine, all the game logic was untrusted anyway - in fact, in some games the actual game mechanic involved live-editing the code of the running game to try and give yourself an advantage - without ever causing a syntax error and while others are also live-editing the same code. Any keystroke causing a syntax error or infinite loop would be an insta-kick for the player who made that keystroke.
If you’re frightened by that, you may be shocked to realize your browser is running unprotected code from random people.
Running untrusted code in a sandboxed virtual machine is quite different to on a native CPU
It's actually very protected, no?
Still basically an infinitely larger attack surface than what OP describes which was fancy wording for some basic IPC primitives to synchronize some game state.