It is indeed working badly and it is hard to comprehend by which actual metric it sorts them. Perhaps it is partially broken and federation doesn't collect all used hashtags?
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Yeah, my guess is there's actually something broken. People can't seriously be talking about what day of the week it is more often than what's actually going on in the world.
Why wouldn't people talk about the boring stuff more? You can click through the hashtag to see who's talking about it. The bird site probably blocks #wednesday from trending to avoid the banal stuff
The other issue is that the default is for the instance admins to have to preapprove every tag before it can trend visibly, which makes sense but isn't going to get you by-the-second trends about unscheduled volcanic eruptions
I dunno, it just seems odd that the trending tags would be so focused on what day of the week it is.
This is the first I'm hearing about instance admins having to approve tags, though. That would certainly explain the lack of topical trending hashtags.
This is probably one of the main reasons I don't use Mastodon more. I was always a casual Twitter user and I would follow a few sports accounts and check out what was trending that day.