By default, Lemmy allows downvotes globally. However, when a server disables downvoting, it is similar to using a feature that is usually reserved for enterprises and very small, non-federated communities.
If a user prefer to not see downvotes, they can disable it by his favourite client settings, but the rest of the community should not miss this functionality for the pleasure of few users.
I like being able to downvote using my main account, but on lemmynsfw it really needed to be removed. People were downvoting literally everything that didn’t fit into their fetishes, so anything that wasn’t straight and and vanilla would go into the negatives. Like, I’m not into mascs, but I still think they should be able to post to gonewild. Even posts in gay-specific subs were getting downvoted en masse.