Research Fellow on Paper They Did Not Contribute- Solicited my Mentor 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...
Putting an asterisk by his name and mine saying we share first co-authorship. 


That alone, on a draft shared for comments, would have been enough to anger anyone. In my opinion this RF is trying to carve a space in the paper by discrediting the quality of your work, which is unprofessional. The quote is also irrespective of any actual problems with your work - assuming the RFs suggestions have some merit - and any self-respecting academic would flat out refuse, unless it comes with an extensive research plan.

The behaviour you describe is so crude that actually improves your position. However, the personality of your mentor and your relationship with the mentor does weigh in. If you have a good working relationship with him, the issue can be resolved with a polite, honest and most importantly calm chat. The fact that he shared the draft without you knowing is not problematic, in my opinion, as academics do so very often. The liberties taken by the RF, however, may hide something more than a request for feedback - they go beyond a bad report. You cannot know, and you should not jump to conclusions, but you should be cautious, suspicious even. 

Some arguments that are generally valid, but for them to work you would need to stand as a professional academic, not a student:

1) Adding a co-author dilutes everyone's, but particularly your, contribution. Both you and the data-editing colleague can argue that you are not willing to add a 4th co-author (field specific), and for an entry-level academic first authorhip is very important and you are not willing to share.

2) The paper is mostly finalised and the suggestions are not substantial enough to warrant co-authorship, plus a debate on the most factually wrong comments (irrelevant self-citations etc). There is not enough work left and you are not willing to consider a change in direction due to time constraints and the distraction it will cause you.

3) Brush off presentation comments by saying that they will be corrected in the finalised version and insist that polishing up does not warrant a co-authorship, especially first authorship (similar to (2))

4) (very context dependent) Express some surprise on the nature of some comments and point out to their relevance. If you want to be cheeky, ask why the RF would be interested in participating in a paper he himself criticised so harshly.

It is important for you to be the one that frames any discussion as discussing feedback on a draft and you have not even considered co-authorship. If you are presented with the idea, e.g. in an off-hand comment, just say "no". If pressed further, politely yet firmly keep refusing. This is where your mentor must take a position and either drop the issue or force you to accept a co-author. If the latter happens, I see two options.

The first is to withdraw your participation in the draft. You are perfectly entitled to do so and maintain agency of your work, but I understand this is difficult from someone in your position and may cause further frictions and issues. The second is to accept (grudgingly), but by stating very clearly and in a non-negotiable manner that the RF will be responsible for any additional work and you will not be adding anything more to the paper, especially results/ experiments. Even if you receive some drafts or emails, you can politely repeat your stance. This is confrontational and also not desirable, but at least you will not be exploited.