It's not really for me to say what abusive flagging is in general, just like I wouldn't be able to say what makes a good quality or up-vote-worthy. There are plenty of people who have their own idea, so just like with up-votes, it's up to them to decide. I'm curious to see if there is anything to it that people can agree on. If there is, this proposed tool could work for them. 🙂

On your second point, I'd also love to see custom filters, it's something I'd love to add my voice to proposing at some stage when the steemit.com frontend team are more up for suggestions, or perhaps building a light tool to filter according to custom criteria as a separate thing. I'm already doing some nice filtering with the voter bot I made, I'm going to be pulling the metrics engine as a separate thing, the idea is tracked here.

Perhaps niches groups could run their own tiny Node.js server for it? 🤔