You are right, ELO doesn’t quite fit.
I guess what I was thinking was just a generally weighted system and ELO was the one that came to mind that used that concept.
How I see it:
You have a baseline of points, say 1k.
@ 1k you get a 5x multiplier to points you get (to incentivise new users)
@ 2k - 2x multiplier
@ 3k - 1x multiplier
@ 4k - 0.5x multiplier
@ 5k - 0.1x multiplier
And you lose a set number of, say, 100 points per day, though you can never drop below 1k.
Additionally, to get the first 1k points:
You register - 100p
You go through the tutorial (showing guidelines, teaching how Slant systems work, etc.) - 900p
Where points show how good you are currently, badges would add lasting accomplishments.
You can hold 3k+ points for a week? Badge
4k+ points for a week? Badge
For a month? Badge
Get most "thank you"s? Badge
Most contributions within a category? Badge
Etc.
Edit: I should add that the baseline should probably be a lot higher and the weights to kick in after certain number of criteria - so that an everyday contributor would start feeling the effects of weights after, say, a month and someone who only occasionally adds content would not feel them at all. So the weights basically start becoming a thing when reaching power-user amounts of points.