"Planar geometry" here is 2-dimensional Euclidean geometry, usually used as Olympiad geometry problem, its objects just be a bunch of lines and circles, it has no Combinatoric aspect and not used to solve another research problem like convex geometry.

Is planar geometry question suitable for MO? This type of question usually can be solved just by a computer and almost have no relation to other field of Mathematics.

Sometimes I see planar geometry on MO and it annoys me a lot because I can't understand what its research value is. Moreover, it even has some upvote! Example.

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typesof questions are or are not acceptable. But, in the end, if a question has more upvotes than downvotes, then that means that the community has received it overall positively, and that is probably the only real way to judge its appropriateness. $\endgroup$