Agreed, and I have more arguments against commit signing.
- Commit immutability is undesirable, and mutable commits are not compatible with signing. For instance, pull requests are squashed and rebased to keep linear history, and changes are cherry picked around. It does not change authorship, however it changes hashes and invalidates any signatures. Or, say, one wants to adopt an otherwise FOSS project which though contains some copyrighted material in its repository, which needs to be
filter-branched away, again invalidating the signatures. - In our world where stuff randomly gets criminalized I prefer to avoid being undeniably linked to my code.
BTW this topic has common considerations with now mandatory (on GH and more places) 2FA. For the latter reason, and also for own convenience and for reducing risk of losing access to your account (which I assess as much higher than risk of leaking my password to third parties) I make second factor public, effectively reverting to 1FA.