Anyone can set any name and email on any commit. Signing is a basic way to have some defence against people forging your name and email for commits. That's it

Anyone can set any name and email on any commit. Signing is a basic way to have some defence against people forging your name and email for commits. That's it. Whatever "signing" means in other contexts is just semantic wordgames. Witches have come out of the inquisition less tortured than all these analogies about "signing" in different contexts. Everyone understands that "signing" in "signing a commit" means something different than in "signing a contract".