You are right, you shouldn't wax/polish matte finish. But swissvax do a special wax just for matte finish 'Opaque' 50ml, bit expensive but it only needs applying 1-2 times a year. I got it originally for the matte graphite Street Triple I used to have.
Ah, cool! Will keep that in mind for if/when I get the new matte grey Speed Triple, or any other matte bike