There’s at least two plug-ins for user reputations which might be useful to you. There’s also a lot of potentially useful discussion on a range of related issues, features and reporting.
The Discourse philosophy tends to discourage this sort of activity.
Here’s one topic on that from 2015:
But Discourse does have badges which may be useful
The badges score things like number of posts and likes.
Here’s the discussion behind them (2016):
And Discourse allows querying the database
Site admins (and soon other users) can produce Data Explorer reports directly from the Discourse database:
There have been several discussions about user scores and reputations
Such as these from 2015:
Plug-ins do exist that may be suitable for you
A reputation plug-in (2016):
A plug-in has been privately developed (2018) but it has not yet been published: