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.
In that situation, what function do the upvotes serve in the first place? If the potential audience already knows they’re going to read and enjoy more content from the same source, do they need to see upvotes to tell them what they already know?
(Remember that without effective permanent karma, upvotes only serve to call attention to particular posts or comments in the short term.)
Comics are usually posted in general comic spaces. A comic that has a following is probably better than one that doesn’t, so those ones should still be bumped up in those spaces. Plus, not everyone follows individual creators even if they like and upvote all of their comics when they see them.