When your partner is a significant hot sleeper it affects both of you. They wake up overheated. You get woken by their movement. The blanket gets kicked off. The thermostat becomes a negotiation. Here is how to solve it practically.
Understand the Problem Is Physiological
Your partner is not choosing to overheat or to kick the covers off. Their body generates more heat during sleep than the standard bedding setup can dissipate. This is not something they can control through willpower and no amount of adjustment on their end without changing the bedding will solve it. Understanding this makes the conversation about solutions easier.
The Separate Blanket Solution
The most effective solution for couples with different temperature needs is separate blankets. Your partner uses a cooling blanket sized for one person. You use whatever warmth and weight you prefer. Both of you sleep under your own blanket on a shared bed. No more blanket stealing. No more one person waking the other by adjusting covers. No more thermostat negotiations where neither person wins. This is the standard approach in Scandinavia and it is becoming increasingly common everywhere.
Your Partner's Cooling Blanket
For your partner the Stillwell Cloud is the most effective option. 100% nylon cooling fiber, Q-Max 0.40, cool on both sides all night. When they are not overheating they sleep more soundly and move less during the night, which means less disruption for you too. See The Cloud here.
Thermostat Compromise Becomes Possible
With separate blankets the thermostat becomes less contentious. Set it to a temperature that is comfortable for you. Your partner's cooling blanket manages their temperature independently. Both people can be comfortable without the thermostat being a battleground.