I am in a situation where I do not know how to tell my mentor I am not comfortable with a research fellow on our paper as an author. I came across a "call to submission" for a paper, in essence, there is a special edition of a journal over a specific topic. I wrote the complete manuscript thinking it was presumptively thesis material but it felt short of novel methods warranted by my academic committee. However, my department eagerly anticipates it is good-quality publication material due to its findings. Anywho, I wrote this paper independently and included a colleague who edited parts of the data analyses as an author. He, unbeknownst to me, sent it off to a research fellow at our institution for his comments as a co-author. The comments are toxic, gaudy, and do not display an adequate understanding of the topic. Worse, however, is that the research fellow is cordial with my mentor, and e-mailed him his comments, selling the manuscript off as his. He has a moderate amount of paper at the institution, and I want to interview there for further training opportunities and do not want to compromise my bottom line. His comments include:
Asking me why hadn't I spelled out multiple abbreviations that are literally spelled out and defined in the sentence or paragraph before.
Putting an asterisk by his name and mine saying we share first co-authorship.
Requesting multiple self-citations over introductory statements known to all, the self-citations are very low-quality non-indexed review articles in openly predatory journals.
Crossed out my name as corresponding author and put his contact information, as he was "invited" by the journal (our whole department got the same call to submissions paper).
When I quote other previous experiments in a similar domain, he has written: "stop changing your hypothesis".
Says my graphics quality "if submitted to a conference, would automatically result in denial of the manuscript regardless of the content"
Is literally editing multiple metrics out and is replacing them with metrics that I have not used and are in fact, the wrong analysis for this experimental design.
Am I overreacting? I feel as if I am in a bad spot. What is the best course of action to remove this individual from the paper without trying to get my mentor involved? I need to ask my mentor for a letter of recommendation in a few months, too. I am a lower ranking than the fellow as well...