Is there really a difference between anal insertion and anal penetration? It seems to be used most, though not exclusively, for images where there is an object being inserted, rather than a penis or tentacle. I personally think it should just be aliased to anal_penetration and let the "dildo" or "butt-plug" and other anal toy tags do their job.
Edit: Also, I've noticed there are a LOT of images tagged anal, but not anal_penetration that depict penetration. I added a proviso to the "anal" Wiki to make it clear that tagging something "anal" is not the full job if there's something going up the butt.
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