We're in the middle of a major re-write of the entire flagging system. As part of this, we're re-thinking how flag weight (and thus "hell bans") work. Anna & I have been discussing this for a while - here's what we're looking at doing instead:
Only look at folks who cast at least 10 flags a week. There isn't much point in doing much to knock the priority of flags from people who rarely flag anything.
If at least 10% of your flags from the past 7 days were declined, you'll get a little warning next time you go to flag something... Along with a link to your flag history so you can see exactly where the problems arose.
If at least 25% of your flags from the past 7 days were declined, you're blocked from flagging anything. Depending on when and how those declined flags were cast, this block could last for as little as a day, and won't ever be longer than a week.
Over time, the flag system has evolved from a rather opaque "I saw a problem, please do something" system into a way for everyone to work hand-in-hand with the elected moderators. For this to be effective, it must include feedback on how well you're flagging - closing that feedback loop should help our more prolific flaggers to become better at flagging, and reduce noise for the moderator teams.