Showing up regularly is good. As is reading, starting, and replying to topics. And giving Likes and Inviting others.
I think the number of helpful Flags would be a good indication that a member is familiar with a forums policies and cares about the health of the community
https://github.com/discourse/discourse/commit/e74b9ee5da8cc7c436b0f0bc6798bbfd93cf9091