Reproduction:
1. Open MED
2. Open Skin Editor
3. Import a small (for the best effect, <16px) skin
4. 'Enjoy' - half of pixel at each side of texture is not taken into account.

This effect is the most noticable if you will try to wrap a cube with 4x4 texture. This is how it looks:

Notable thing is that preview window displays texture correctly - it's only a bug in 'textured rectangle' drawing on left side.
A image of 8x8 image (just the same one tiled 2x2) can be seen below. For better comparsion, I replaced one quarter of texture with a stretched version of original image (that is aproximately how it should look):


While this is not a critical bug, it causes (different) precision loss when mapping models with MED.
Models with large textures barely suffer from this, while on small textures it may confuse the viewer about placement of contents (vertices and triangles), causing one to re-arrange them and find out that they don't match on 3d model now.