Stop thinking in terms of "votes". Think of the activities as a "fixed content messages": John liked this. Alice liked that. Bethany did not like that other thing. Each "vote" is a meaningful interaction. A server that says "2734 people did not like your message" means absolutely nothing.
This is not a political council nor a popularity contest. No one will make critical decisions based on the amount of worthless Internet points.
I do not understand arguments about privacy when we are talking about a public, social network. Social interactions online do not need to be that different from real-world interactions. if you are not willing to say "I did not like / I disagree with you" to someone personally, then you shouldn't say it at all.
Ok.I see. Personally I don't think it's a good idea. It's only a marginal benefit in terms of protection against data scrapers (you can also build that profile based on who they follow, or what they write about...) and it makes things more difficult for moderators and hides important information from other community members.