I've only answered a few questions on SO, but my rep keeps on growing as people upvote them. My rep there is definitely not indicative of my actual involvement on the site.
But it is indicative of the value the site's users have received from you over time.
Reputation is difficult, and I can't think of a good way of doing it, but SO's way is not really any worse than any other site. And it's a lot better than counting "likes" on Facebook.
I was super into it for a while, but that time ended many years ago. Ever since then I occasionally pop by, maybe answer a question or two and do a little bit of moderation on the side (mostly in the edit queues).
Yeah same here, over 90% of my reputation score is from a single answer, years ago,that frankly isn't even all that insightful. It keeps getting upvoted though, so I keep adding 50 points a week or so even though I haven't really participated much in a while.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.