This feature is Kagi's single best innovation in search. It's what makes their results so much better than Google's: where Google's results are usually drowning in garbage websites, Kagi comes built-in with a great set of spam filters, and on top of that you can adapt your own personal list of good and bad domains as you go!
I have been using this with ublock for a long time. It actually makes me wonder if that is the reason I dont have the complains about google search that I read about here