Is this for an online community like Lemmy, or more oriented towards fixing the credit institutions?
in any case, a credibility metric would soon turn into a goal to achieve ^(karmafarming says what?)^
A metric ceases to be useful when it becomes a goal.
Perhaps «monitoring» was too strong of a word...
I'll rephrase: if a layperson wanted to check if an instance is not following through, how could they confirm it?