How to handle Co-author who is not listening the suggestions to improve the paper quality

In every scientific paper that I have been involved in, there has been opportunity for co-authors to directly edit the manuscript themselves, if they wish to make a contribution. If you feel that you have suggestions that are not being taken up, I would advise you to ask something like:

Would you mind if I did a pass on the paper to edit in some of the suggestions I've made?

If your co-author hasn't been editing in your suggestions because they are unclear, overloaded, or not able to do so, this will give you a chance to adjust the paper in the ways that you want. If, on the other hand, they actually disagree with your suggestions, then they may not want you to edit them in, and you can then actually have a discussion about whether and why the proposed edits should occur.

In short: I believe that you need to shift from being a passive critic to being an active contributor who provides actual text that accomplishes what you want to have accomplished.

I have had this problem on a few occasions. Usually I got ignored over suggestions on points the lead author did not want to discuss directly because (i) s(he) felt (s)he was on the right side; (ii) s(he) felt (s)he was on the wrong side but wanted to push their version nonetheless; (iii) s(he) felt I was not in a position to criticise that part.

In all cases I demanded for an explanation, and this is why I can answer your question here. So, my first suggestion is that you contact this person demanding an explanation. (Mind that most people don't do these actions -- questioning parts of manuscripts where they are co-authors, and later seek to understand why they got ignored -- and that most lead authors prefer having passive "co-authors".)

How did I react in such situations described above? I will briefly explain:

(i) I tried to make my point clearer, which subtly meant I was trying to prove the lead author wrong. The lead author always insisted on their point without seeming to listen to what I said, while emphasising on how they took my suggestions on other points. I had to let these issues go, and they got published, and as a result I do not fully agree with some of the papers I participated in.

(ii) I insisted. This will make the lead author uncomfortable, and you will have to make sure this person understands you're not cornering him/her. Typically there is a clear mismatch with data or logic that the lead author doesn't want to hear aloud. Usually I got the problem fixed, usually the lead author wasn't happy and is now unlikely to collaborate with me in the future. I think that is OK, given the circumstances. Once I had to let it go.

(iii) This is the most common situation. Typically it involves a collaborator from a different field under strong influence of their bossy PI, where you're not sure which of the two is doing the writing or even answering to your emails. They do not appreciate being questioned "on their turf". You have to consider the possibility you're wrong there. Which I think is irrelevant, because if you are wrong then there's all the more reason you deserve a clear, logical answer. In such cases I insisted, and was authoritatively told to "keep to my business". I insisted again, and got ignored, and had to let it go. Usually the lead author apparently did see my point but was told by their PI (i.e. the last author) what to do. As a result the lead authors in these cases made sure to communicate they were open to collaborate with me in the future, while their boss cut communication.

Anyway, hope that helps. In the long run you're selecting whom you can work with.

There are at least three possibilities here:

• The quality of your feedback is low. You might be wrong, incomprehensible, or nitpicky. Ask for feedback on your feedback.
• The lead author is unable or unwilling to do a good job. In this case you should do more for them or withdraw your coauthorship.
• There is a third author who is giving advice which contradicts yours. It might be important to the lead author not to upset this third person, so they might not admit this to you. The solution is to talk to other authors.