It's fairly common to see discussion of different chirality for amino acids and sugars whenever people ask for advice on plausible alien designs or biochemistry (e.g.: metabolizing left-handed sugars and with proteins made of right-handed amino acids, compared to our R-sugars and L-amino acids). However, I've never seen anyone ask about a species using both chiralities in some way, so aliens who can digest both R-sugars and D-sugars, and/or who who have proteins built from a roughly even amount of R- and D-amino acids.
I've been considering trying to develop aliens who use roughly equal proportions of both chiralities of amino acids to build proteins. My questions then are A) is there any reason life couldn't incorporate both L- and D-amino acids into its biochemistry (this is of more interest to me), and B) could life evolve to digest both L- and D-sugars?