Yeehaa! I found the reason for the odd Fonts on the HUD (generally with Text2D) ;D.
When the character has an actual size of 8x12 pixels and I create a Texture of it, the image data is resized to a power of 2. Then the Texture is applied to a geometry and is then rescaled to the correct size. I simply padd the Texture data to a power of 2 and draw the String on it. Then I fix the wrong Texture size with texture coordinates 8).
Now the Font on the HUD looks absolutely perfect. Check it out.
Marvin