Things that are ConsideredHarmful are things that, while perhaps easier or even more logical, cause more trouble than they're worth in the end. Many times it is not immeditately obvious that things are harmful, and it can take experience and observation to realize it.
The phrase derives from a famous 1968 article by computer scientist Edsger Dijkstra, entitled "GOTO Considered Harmful" (whose title was actually penned by editor Niklaus Wirth). It has been widely copied in later works.
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