The best part of the fediverse is that anyone can run their own server. The downside of this is that anyone can easily create hordes of fake accounts, as I will now demonstrate.
Fighting fake accounts is hard and most implementations do not currently have an effective way of filtering out fake accounts. I’m sure that the developers will step in if this becomes a bigger problem. Until then, remember that votes are just a number.
Out of interest, within a community (that’s what a sublemmy is called, right?) is there any facility to prioritise votes of people subscribed to that community over those not subscribed? Was that the thing with brigading before (sorry, didn’t realise this before!) that mods can moderate and ban posts/posters but not votes/voters?