B&W 802D1 - How can I tame the brightness?

that might be more difficult than hanging a ceiling fan:)

802 D1s need thoughtful placement to perform best. They are not bright and fatiguing in a non-reflective room with the right width and toe angle (zero or near zero). 

Placed in a small room with straight, on-axis toe and they can certainly sound boosted in the upper mids/low treble. Keep in mind that B&W voices their speakers knowing that the vast majority of owners will not have them many feet out into a room but instead have them within a foot or two from the forward wall. The resulting  boundary gain will go a long way to offsetting otherwise perceived brightness. 

If you have tried everything but still dislike them, what is left to do other than cut your losses and sell them? 

If you decide that you can’t live with them I’d suggest looking at Vandersteen upper range of speakers. They might be more to your liking

My 802 D2 was a little tight and sharp on the top end it wasn’t bad. I did what Bill Steveson suggested about 5 years ago. I used 2 JL Audio E 112 sub woofers with a JL Audio CR-1 and the system sounds great for my ears. It took me a while to get  the subs positioned correctly but it was worth it my room is 14’ x 26’. 

Well, one could always make a steel cage to house the 802s - a bit like Roksan did with the original Darius loudspeakers :))

BTW, joking aside, studio monitors usually have a specific orientation unless they are symmetrical such as in a d'apolito configuration e.g. many Focals, or where they mount the tweeter beside the midrange as in the Neumann KH 310.

I've never seen anyone use a pair of Yamaha NS 10s upside down in the studio - and that is a speaker that defines "bright".