When you see how a bike is strapped down on a car-ferry for up to 9 hours ie. on side stand and then a strap across the seat and the whole lot tightened so the front and rear suspensions are compressed you can see how 'over engineered' all side stands seem to be and not just the R1200RT. Therefore using the side stand to mount the bike for the 2 seconds it takes should not be a problem.
I don't use the pegs to mount, but I always get on from the right side for a couple of reasons. First, I think most of us cock the handlebars to the left side on level ground; this firmly sets the balance onto the kick stand side. Were I to mount from the left without shifting the handlebars over, the handlebar and grip (plus aftermarket conventional mirrors I've added) restrict the space and prevent me from leaning forward to allow me to swing my leg over the top of the seat. Second, especially when loaded up with gear on the back seat, I want to minimize risk of over-balancing the bike by directing the energy to the stable, kick-stand side. Similarly, when I have to wrestle the bike in reverse over rough ground by walking it back from the left side, I usually leave the kick stand down so that, in the event is tilts to the right, I can pull it strongly to the left where the stand will prevent if going down on that side. Also, if I have to lift the bike up after a static fall to the right side, I first extend the kick stand to avoid a second fall to the other side. It's also easier than trying to re-mount a laden bike with the stand up. It's a very tall bike and more tippy than previous bikes I've owned, so anything that preserves balance is paramount.