Is it appropriate to reject a manuscript based on language (minor) issues after first review? After 2nd round of review (R1) for almost 2 months, I received a sharp rejection letter for my manuscript (in biology) submitted in a certain journal for language-use concerns and formatting issues. Nearly 80% of the comments raised by reviewer #1 and the editor (I think they are one person in this case) are mainly the use of British-English and formatting, but the journal has no clear policy of the English-use as long as style and punctuation is consistent throughout. English is my second-language but we use it in universities and communications, however, I believe the language concern is not an issue as my co-author (my supervisor) is a native English speaker and we proofread the paper many times before resubmission. Our personal assessment based on experience with other journals, this concern should at least be major or minor revisions.
It is hard to see how ethics enters in to it. Had you paid them something and they rejected it, keeping your money, then it is a different matter. But a submission is just an offer and it can be rejected for any reason. It may not represent the best policy in general, but it isn't unethical.
And, perhaps there are other issues as well and they all piled up to indicate a reject. That is impossible to judge without more information that only you and the editor might possess. It might be as simple as not wanting to do a third round.