Looks like Reddit is getting in on the NFT scene after some previous experimentation with them. They will be using Polygon for this.
"Reddit has partnered with Polygon, an Ethereum-compatible blockchain, to mint these avatars on-chain. You can use Reddit’s own blockchain wallet called Vault — which is available on the firm’s native app — to store and manage these NFTs. Currently, Vault is used to earn blockchain-based community points and spend them on special features like badges and animated emoji."