For example, some holder (maybe a founder) of a certain coin can burn a certain amount of their tokens, making it more rare. This is a quite common practice. If I were to burn a certain amount of tokens, I think the most natural thing to use as a burn address would be the contract address itself.
That's not entirely true. Just look at one of the many burn addresses that people willingly send money to all the time, for example: https://etherscan.io/address/0x00000000000000000000000000000...
For example, some holder (maybe a founder) of a certain coin can burn a certain amount of their tokens, making it more rare. This is a quite common practice. If I were to burn a certain amount of tokens, I think the most natural thing to use as a burn address would be the contract address itself.