Lets say that an instance doesn't allow downvotes called NoDownvotesInstance. That instance hosts a community called NoDownvotesCommunity.

Now, lets say someone on another instance that does allow downvotes places a downvote on a post made to NoDownvotesCommunity. Does NoDownvotesInstance federate that downvote out so that other instance with downvotes can see it, or does it just drop the downvote so that it goes no further?

Edit - @[email protected] has answered this, with evidence. Despite the highest upvoted reply suggesting otherwise, it appears as that instances with disabled downvotes do not federate downvotes on.