Careful miners out there : Some pools are stealing their miners by using the whole block to mint gas tokens. If your pool does this, leave ASAP.
Take this block for example, mined by F2Pool : https://etherscan.io/block/12071965
The block contain only ONE transaction, which is a CHI minting at 0 gwei, most likely a transaction broadcasted by the pool themselves.
Of course, since the minted CHI are not part of the ETH block reward, they are not going to give them back to the miners in their pool.
This is blatant thievery as they're using the money that was supposed to go to miner as block reward to mint CHI for themselves. If you look at the address receiving the CHI, you'll notice that they do this many times every day.
Be careful which pool you join. If they're stealing you, leave asap.