Amethyst has this "report spam/scam" -feature, and the global is also filtered based on the reports of your follows (I suppose). It usually works quite well, and my global is usable even if I am loading from 20+ free relays.
Discussion
Noticed the problem isn't as prevalent on Amethyst. Still unsure how to filter by relays. But learning on all platforms.
I have been advocating for better clientside spam filtering tools (similar post blocking etc.) instead of paid relays. I was suprised to get really bad response from the payrelay crowd. I think the uncensored "wind west" type of global feed is an important feature of nostr.
Thankfully nostr is an open protocol, and one can choose to use the client that has the features, or code his own one.
btw. I found your post from the amethyst global. I did not follow you before.