My 2c: cred as a concept is inherently intersubjective, because it represents a shared subjectivity. An individual’s belief about how credible someone is, or how valuable their work has been, is subjective. Cred is one step further: it’s the communities shared conception of how valuable some work has been.
SourceCred scores are an attempt to make quantitative and explicit this intersubjective reality of cred, and it does this by mixing the objective (who wrote which commit) and the subjective (I liked a post) together. However, I don’t know that the “mixing objective and subjective” is what makes it intersubjective, per se. Since cred (the concept itself) is intersubjective, I think even a version of SourceCred that only used “objective” data would still be intersubjective; it just probably wouldn’t be a very good/useful intersubjectivity.
I recommend reading Sapiens to get more of a feel for intersubjectivity.