True relationship between bones/armature and rigginh Is it true that the armature/bone structure really only depends on the Head of a bone, in particular with regards to rigging/skinning a model?

I am using niftools to import models into Blender, but several of the bones are pointing in the wrong direction. The location/rotation of the head of the bone is fine, it's just the tail is positioned incorrectly. However, when the model is used in-game (Morrowind), everything appears to be functioning properly.
Vertex movements are referred to the head bone, tail position is important only in case of automatic weighting or bone heat weighting, and - of course - in case of IK chain or other connected bones.

After weighting is done, if your bone isn't parent connected with another bone, you can freely move the tail in edit mode (i.e. to align axes with world axes) without affecting the behaviour of the rig.