Sensor damage due to overheating?

The immediate consequence of overheating is an increased noisiness in the analog circuitry and possibly failures in the digital circuitry. There is no immediate damage to be expected before the camera becomes non-functional. However, the longterm consequences are vastly accelerated aging of the sensor, leading to hot pixels, loss of sensitivity, worse noise behavior particularly at longer exposures, and eventual failure of electronics.

While the effects in the analog circuitry are gradual, failure modes in the digital circuitry tend to be invisible at first.

It's the same why people do not really want to buy CPUs that have been regularly overclocked/overheated: they are expected to start having dropouts much sooner than CPUs operated according to design specs.

So take reports of "I overheated my sensor and nothing happened" with a solid grain of salt: it's a bit like "I smoked a cigarette and didn't get cancer" and does not really make it a good idea to follow the "I did not notice anything happening last time, so it must be safe" mantra.