Have you thought about a separate extension that just has a toolbar button that is mostly in a dull inactive state with a grayscale badge, but when there's enough discussion on a page, it both lights up and has an obnoxiously colorful number?

Even though I never mess with it, I find I'm generally aware when there's a badge on my adblocker. I believe that'd be enough to remind people to click it. The heuristics should be strict enough not to light up all the time, or maybe even support user-defined filters for advanced users.

After a while it's possible they'll subconsciously think about Ampie — and the dull badge will still convey "yeah, there's some discussion, check it out."

ps. I say separate extension because I'd be wary of giving it access to all sites and data, which I guess would be required if that was only a setting?