I am currently reviewing a computer science conference paper. I like to give constructive feedback both related to the content as well as for language issues, such as typos or grammatical mistakes.
The paper I'm currently reviewing has significant language flaws. Mentioning each and every typo, wrong word order, and grammar issue would take me about an hour. The paper will likely be rejected anyway, so I am not sure if these language suggestions will even be used. It would be different if the paper were likely to be accepted, because improving the language would further improve the quality of the paper.
Does it make sense to give thorough and detailed feedback on a poorly written paper's language quality in a review if the paper will likely be rejected?
Your question isn't about the level of language in fact. If I understand well, your real question is "Is it worth it to take 1 hour to correct a paper, since it will certainly be rejected ?"
At this question, I will always answer yes. I am personally a non-native english speaker and I love when people correct my work. I can then improve my English, which is always good.
What do you have to lose by doing it ? Nothing. And the person will even maybe be grateful to you.