Interesting. I've barely posted/commented — in particular I've only made seven posts since 2012 (and zero since 2018) — but I guess because signed up in 2010 I'm in the top 17% of users.

Nothing to brag about, but it's definitely higher than I would've expected. The required mental model is different from what I'm used to HN/reddit — rather than posts going stale and/or getting archived, Stack Exchange and Quora are more like social wikis. Writing a popular early answer that happens to remain relevant over time is like writing a high-profile Wikipedia article and then collecting karma on it indefinitely.