I flagged an answer (the shortest one) in this topic since the answerer posted it twice (no matter if it is correct or not), but my flag was declined by moderators with a standard phrase: "flags should only be used to make moderators aware of content that requires their intervention".
If this is not a case where moderators should intervene, then what is the meaning (assuming that has one!) of the celebrated phrase?
Later edit. Someone frustrated by his two days effort to solve correctly a problem, and after giving him a hint (to use an idea which is already present in my answer to this question and which received $7$ upvotes), wrote in his answer: "thanks to YACP for stealing the idea from user3462, claiming to have a proof based on the idea, deleting the claim and saying it didn't happen, getting angry at me for not giving him credit, then getting angry at me again for thinking the idea was worth giving anyone credit for in the first place". I flagged his answer and guess what I've got:
"flags should only be used to make moderators aware of content that requires their intervention".
What is this? I've thought that the answers are posted for answering mathematical questions, not to express our frustrations.