Downvoting is a method of moderation. If a community chooses not to allow downvotes, it had better have plenty of attentive and levelheaded moderators to make up for it. The power of downvoting as moderation scales with the activity and population, making it an indespensible tool the larger a community gets.

Still, whether or not to have downvoting should be the choice of the community. Reddthat ought to be able to make the choice not to have it, if they are willing to put in the work of manual moderation. However, disabling users from downvoting in other instances' communities means taking away that choice from those communities. As things are, I (a Reddthat user) cannot become a fully contributing member of a large community elsewhere, if that community relies on downvotes to help moderate.

Downvoting can be abused, but then again so can upvoting. If I choose to make a community on Reddthat, I'll say that I would prefer to be allowed to use downvoting to help moderate. My feelings are much stronger when it comes to downvoting on outside instances: if Reddthat prevents users from participating in outside communities, those users will have no choice but to find another home for their Lemmy account. And since users can only create communities on their home instance, that bodes unwell for the growth of Reddthat.

I agree! Unless we want the artist community to hate us, it should be a bedrock rule that any post includes both (a) the artist's name, and (b) a link to the artist's original source in the body/comments (typically twitter, pixiv, artstation etc.). There's a good reason this was a rule in every big art subreddit.

A useful tool is the SauceNAO reverse image search. It's really good at sourcing anime art specifically.