Well it's actually only Admins and instance-level moderators who can do it at the current time. Regular community mods can't see them or pull them up, at least not in the current version of Lemmy.

It was his main comment which had the votes slashed, it was sitting at -40 but was slashed to -30. Speaking in terms of raw downvotes not just score. The +42 score it had didn't change at all.