This is also a problem for enterprises. I’ve seen commits from root, ec2-user, etc: GitHub knows who’s pushing a commit even if git doesn’t, and it’s maddening that at least for enterprise accounts they don’t carry that identity into the metadata.
(Not sure if such a field already exists in the commit blob)
That's not how git works.
This design doesn’t preclude the usage of additional information in the commit blob that isn’t used to compute the hash.
(Think for example how file access times do not affect its hash)
https://git-scm.com/docs/git-notes
"Adds, removes, or reads notes attached to objects, without touching the objects themselves."