How to handle translation issues in answer or some part of answer is wrong or an altogether wrong answer?

Question

Can other users comment on such posts to point out mistakes or translation issues?

From latest discussion on such issue, OP told me that one can share what he thinks is the right answer (by posting another answer) but should not criticize others for their attempts to answer!, is there any rule which says one should not comment to point out mistakes in answers?

If one can (which should be clear whether other users can comment on such issues or not after answer to this post) comment pointing out mistakes but what if OP doesn't take any action?

It seems flagging such answers is not allowed because I raised flags on some wrong answers but they were rejected saying

flags should not be used to indicate technical inaccuracies, or an altogether wrong answer

I also raised flags for answers which I feel are offensive to particular group of people but those were rejected saying

information relevant to the question, accurate or not, does not run afoul of the Be Nice policy

If someone writes any objectionable thing towards some group of people or translation is completely wrong or answer is completely wrong then, what's the use of keeping that on site and why moderaors can't take any action on such issues?

Answer 1

Can other users comment on such posts to point out mistakes or translation issues?

Yes, they certainly can because that's what comments are for. But some people prefer to downvote instead of leaving a comment.

Is there any rule which says one should not comment to point out mistakes in answers?

There is no such rule. On the contrary, constructive criticism is recommended. But make sure it doesn't turn into a comment-war.

What if OP doesn't take any action on your comments?

There's nothing you can do. You cannot force someone to correct their answer. What you can do instead is, write your own answer which is "more accurate."

If someone writes any objectionable thing towards some group of people

You can downvote and/or flag the answer. But if the answer is objectionable only because it's directly addressing a question, the problem maybe with the (opinion-based) question and not the answer.

translation is completely wrong or answer is completely wrong then

You can leave a comment, downvote and/or vote to delete.

Also see What exactly is a "wrong answer"? What is the official policy on handling wrong answers?