The power meter, which is with the speedometer, has an indication if battery output is throttled. You can also feel it in the accelerator, no need to look.
Wait, the car doesn't tell you if the battery is overheating? That doesn't happen with Li-ion batteries? I heard it does in cars and airplanes and laptops...
If the battery is physically damaged causing a runaway, the car flashes a huge warning and beeps. But that isn’t caused by ordinary events like driving up a steep hill when it’s hot out. It’s caused by accidents that significantly damage the car.
Battery failures can also be caused by manufacturing/design defects in the cells (as in the Boeing batteries) or malfunctioning components of the active cooling system in the Model 3 like fans/pumps/coolant (like the Tesla club owner).
Having a coolant temperature gauge in front of you could show you a trending problem, before the car announces to you that it is shutting down as you attempt to merge into 75 MPH traffic.
I don't think the Boeing failure would cause a runaway in a Tesla battery, nor any other electric car allowed on the road, nor in the redesigned Boeing 787 battery pack.
The Tesla club comment at the top of your link is about a Roadster, not a Model 3.
https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_...
https://teslamotorsclub.com/tmc/threads/overheating.109238/