Even with the Hashtag misuse that’s not as bad as group spam, since people spamming groups can reach further than they otherwise would just spamming on their server. Which is why being able to moderate groups is important. Also with Guppe’s system you can create any group you want without authorization, that’s a problem because malicious people can create groups that aren’t acceptable including ones with racist and illegal content and use it to distribute that across the network. I found a few of these without much digging and I quickly reported them to Mastodon.social and got them suspended but they’re still there on the other servers.
I don’t know how it is on mbin but on Lemmy the best thing to do is message the admins directly, and not bother reporting. This is because Lemmy’s developers give way to much credit to the legitimacy of forum moderators and do not allow a way for reports to only be sent to administrators, meaning that community mods like these can easily dismiss reports before they are seen by admins. So best thing to do is message them directly at the current time.