Actually even if it's not HID as long as the car behind you is taller like vans, pick ups, tendency is their head light beam will reflect directly to your rear view mirror. So you need to tilt it, no need to cover it. Besides during night time it is advisable to tilt you rear view to avoid glare.
I've been an HID user ever since the xenon bulbs days, it's just like a normal head light. You can flash other cars as normal, just practice driver courtesy of course... especially if the car in front of you keeps flashing maybe he is all dazzled up, just turn it off.
MMDAs / officers have nothing on HIDs as of now AFAIK.
No need for a clear crystal type head lamp, your non clear type will work just fine.
In my own humble opinion, just go ahead w/ it. Especially since you said the village your in is not well lit.