the problem with brands creating mastodon accounts is that they can just publish directly to ActivityPub instead of using a mastodon instance's resources to publish themselves
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like, there's not really any reason they couldn't if they already support technologies in their publishing platforms like RSS
this would dispel the idea that there is an acceptability pattern for what is allowed "on Mastodon"
i would reject it. many would reject it. some instances would reject it by silencing it from federated timelines. but it's a much more useful application of the technology, especially for more less informal publications apart from microblogging, like art galleries.