I'm a PhD student with two supervisors, one main PI which I has nothing to complain about, and a "co-supervisor" that had a long history with my PI. He was my PI's student, then post-doc, then worked in industry for years and came back as an assistant professor.
I barely talk to the co-supervisor beyond first year, and started to notice he puts in minimal effort into research and supervison - only giving wording suggestions when reviewing papers, doesn't providing anything more than "Have you tried AI?" or "What's your plan in 3 years" kind of feedback.
Other students are complaining about him being very pushy on publishing and cares much more about quantity than quality - suggested another student to submit to an irrevalent journal because it is "faster" when the student is aiming for the best in the sub-field.
All in all, I think he is much suited as a manager in industry or a lecturer than a researcher. However, because of the co-supervision title, he asks to review all my papers and becomes a coauthor by providing feedback that are exactly the same as the ones Grammarly provided (and I meant not similar but word-to-word the same as Grammarly and nothing else).
I realize it is academic dishonesty to let someone that didn't contribute to be a coauthor, but I'm not ready to be on the bad side of him, and potentially my own PI, this early on, especially considering I hope to go into academia after. I'm thinking about talking to the department chair, whom I trust, privately after graduation, which will hopefully be taken into account to some degree during his tenure review. Is there anything else I can do in this situation? Am I wrong to think he is a fraud?