One thing to keep in mind is they don't federate with kbin.social; so they can't see your posts or replies, and can't reply to you. I believe your upvotes won't federate (maybe to other instances, but not to theirs at least). Downvotes work the same as they do for any other post as those don't federate in kbin to begin with. One-sided federation in the fediverse seems like it can be a bit confusing to users, I'm not sure in what case it's a good idea in since it can be like talking to a void.