The Award system in Reddit is a better comparison than the rating/upvote system there.
You can upvote every single post in Reddit without being restricted, however in Award you're limited to how much Award you can give to a post and you need to buy them using Reddit Coins. That is pretty much close to sMerits as well except you don't buy them obviously.

They give free Award randomly sometimes and it is randomized on what Award they can let you give to a post. I commonly get the Bear Hug award, lol.