Upvotes/downvotes are usually for the approval/disapproval of the comment itself so it would be best to upvote a comment expressing your opinion or write your own if there isn’t any.
AFAIK, Krita’s more oriented towards 2D illustration than image editing.
Can you have it only write one way?
This can be configured on the web UI at least.
The public downvotes on kbin definitely reduces the incentive to mindlessly downvote comments and can even be useful for moderation.
Voting is an easy way for someone to share their approval or disapproval if they don’t have any further comments. I would rather retain voting than have a chain of “+1”, “agreed”, etc. replies under every comment.
It could be brought up in a feedback community or feature request page if it exists.