Honestly I wouldn't want anything baked into the protocol, but I can see people donating small amounts to the instance hosting a worthy comment if there was a simple enough way to do it.
Cryptocurrencies were supposed to enable that, but I think we are still a long way away (no, lighting does not qualify).
They are two separate projects with similar goals (implement a Reddit clone). They both use the activitypub protocol, so they can generally interoperate. Other activitypub based services, such as mastodon, can also interact with either Lemmy or kbin, but in a more limited and clunkier way.
Lemmy was started first so there are more servers and more users, kbin is more recent.
Honestly I wouldn't want anything baked into the protocol, but I can see people donating small amounts to the instance hosting a worthy comment if there was a simple enough way to do it.
Cryptocurrencies were supposed to enable that, but I think we are still a long way away (no, lighting does not qualify).