I've spent the past week talking to a number of moderators and co-workers, and thinking about how this should work. Based on that, here are the problems I feel need to be addressed:
Lots of folks don't have a solid grasp of the jargon here. "Helpful" is self-explanatory; "declined" considerably less so. Stuff like "aged away" or "disputed" is almost opaque. So giving folks a page that lays out the mechanics of banning (as you ask for) doesn't help very many people; it's giving someone the factory service manual to their automobile when they just wanna know which blinking lights mean they gotta take it to the shop.
Even experienced users can misunderstand how "bad" a declined flag is, or what a useful reaction to it might consist of. Some of this goes all the way back to the "flag weight" days (ancient history!) but a lot of it is just that we've... never really explained it in the UI beyond "please review these flags".
We need a consistent path for learning when it comes to bans. To understand a ban, folks need to understand declined flags; to understand declined flags, they need to know why they were declined. So they need to view their declined flags, then view instructions on interpreting them, then probably view the posts / comments themselves.
So I started by writing a help center article on declined flags and flag bans. It spends a lot of time talking about things that contribute to declined flags, and just as much time talking about how to process them. And then a very small amount of time talking about bans, with the focus heavily on what you do after the ban is up.
That just leaves wiring this guidance into the UI. We wanna be careful where we link to this article - ideally we don't send folks directly from the "you're banned!" message to the help center, we route 'em through the list of their declined flags first.
With that in mind, I've made the following UI changes:
All "you've had recently-declined flags" messages (bans, warnings) send you to your flag summary with the showDeclined filter active (all flags declined in the past 7 days). Yes, even the one in /review, which previously didn't link to anything.
The flag summary itself has a sentence or two of guidance at the top of the flag list for every filter: either it explains the purpose of the page, or it explains the meaning of the status being filtered on. So for recently-declined flags, it explains what a declined flag is... And links to the new help center article for the full explanation.
The "you are banned" banner on the flag summary page (which appears at the very top of the page if you visit it directly while you're banned), links to both the recently-declined filter (current behavior) and the associated help center guidance, for the benefit of folks who stumble onto it via their profile.
...oh yeah. And there's a handy new /users/flag-summary/current path that redirects to the current user's flag summary, to make explaining this stuff and supporting folks on meta a bit easier.