I genuinely think it's not ok even then. Copilot is a tool, one of many I use. That tool has no business polluting commit messages without my knowledge.

The appended message isn't even adding any new information, as in this day and age a vast majority of commits is probably "co-authored" by an LLM.

I should have been clearer, the hidden addition is never ok.

If I ask Claude to write a commit message, it will inserted a co-author line (and an ad), but I can see it and disapprove, add a counter instruction to CLAUDE.md etc