From the UI that pretty much copies Reddit’s in the regard, it would seem that yes. However, the votes are actually not secret. Maybe they were when they were local, but now they are transmitted to the federated instances. From other platforms, like Friendica, one can actually see the votes as (dis)likes. I can see your votes.
Because of Lemmy’s UI, it is very easy to believe that the votes are secret, and many users probably assume they are. For example, I am quite sure the ones who use an alt from another instance to double-downvote do make that assumption. I think this fact should be disclosed in a clear way, at least in the instances’ sidebar, if not in a banner.
From there on, I see two possibilities:
As a Friendica user, who is used to like as a public appreciation mark, I am naturally in favor of the first option, but that is only my personal preference.
If the second one is preferred, it means that the other admins should never receive the voters’ identities. One should not trust the other admins to just not display them. In fact, I think “never trust the remote admin” should be an important rule in the fediverse, an instance should generally protect its own users rather than expecting others to do it in its stead.
In that case, I think it would be appropriate that “Vote” should be an disctinct activity from “Like”, and in particular one that cannot be federated with the authors name. Maybe it could be a private thing sent to the Group, who in turn sends a IsVoted activity? This is pure fantasy, I am not qualified to suggest an actual implementation, I just think it should be distinguished from other platforms’ public likes.