mismatched threading

Things going through one hole and then coming out the other, much like with regular threading, but where nothing should connect the holes together and no reason is given for how this is even possible.

These orifices are normally considered matched (deviations from these are expected to be tagged as mismatched_threading):

mouth <-> anus
urethra <-> urethra (urethral all the way through for characters with two internally connected urethras)
nipple <-> nipple
ear <-> ear (in one ear and out the other)

Vaginal threading is almost always mismatched. If there's any sign that a "shortcut" was taken by puncturing organs (usually blood), you're dealing with impalement instead, possibly fully impaled,