Well, as mentioned that is also covered by the Monthly Active Users metric that already is available. But in addition to that, I think it would be interesting to see the number of users who read and vote but don't post or comment. Even though posting and commenting is the biggest part, actively voting is still an important part of the ecosystem.

Do posts get marked as read when you read the comments? There's the x new comments feature, so something must be storing that timestamp.

All three of those work in Thunder!