What are the criteria for using the phrase "in Judaism..." in an answer?
I used it myself when answering to newcomers, but when it is legitimate and when it is not? Do we follow the majority, the Paskened Halachah etc?
The beauty of Stack Exchange is that you can basically write anything you want in an answer. As far as I know there are only a few things that will disqualify an answer:
As long as your post attempts to answer the question asked, is somewhat discernible, and does not violate any rules, you can say whatever you want. You can say “in Judaism...” or you can refrain from saying it. You can compose an answer that is entirely correct, and you can compose an answer that is entirely incorrect.
However, there is a built in system to deal with these possibilities: voting on the answer. If people think your answer is good they will probably upvote it. If they think your answer is bad they will probably downvote it. Your use of “in Judaism...” might be a factor that users consider when deciding how to vote on your answer. If you claim “in Judaism...” and other users feel that you are misrepresenting Judaism, they will probably downvote the answer. Even if it’s not a total misrepresentation but merely an oversimplification or generalization people will likely downvote it.
So if you feel that something warrants a claim of “in Judaism” then by all means say it. The votes will then function as a sort of “peer review” to see if the community agrees with your presentation of Judaism. If you find that you consistently receive downvotes on such answers then you can either refrain from making “in Judaism...” claims, or simply reconcile yourself to the fact that other users may have a different understanding of Judaism and downvote your answers accordingly.