Tilting B&W 802D speakers slightly forward or backward

This is an excellent question, and the answer is you want the tweeter to point at your ears or above your ears.  Not below.

The exception are speakers where the tweeter is not the top driver. 

The B&W speakers in particular just sound better when the midrange points at your head and the tweeter points above your ears, and probably so that they cross behind your head. 

The explanations are  found in the vertical dispersion and the complexities of crossover design, but the beautiful frequency response curves go to heck above the tweeter with most speakers.

Fortunately this is super easy for you to test.  Just listen.  Sit a little lower and see which sound you prefer.

Only the B&W 802F, never the B&W 802D!

(sorry)

I always tilt my speakers backwards, unless they are on a stand above my ears.

Why would you tilt them forward?

Its a good idea. If I had a pair I would try it and get back to you. You need to find someone that has these speakers and will let you experiment a bit with them.

Why do you feel the need to tilt them?

I own the 803D3. 

They don't seem to be designed to be tilted.