I think RSS feed reader users are also unaffected by flags. At least hnrss.org feed followers are. I haven't tried news.ycombinator.com/rss. But as long as the post hits the RSS feed before it is flagged, your reader can pick it up.

Honestly, for me, most of the time I am not interested in the flagged posts, but if you are, RSS is another way to see them.