I'm also not all that obsessed with wondering whether or not how I wipe my ass is normal. For me, it's not a question of normal, it's a question of "is there still poop on my ass or am I done wiping", you know?
I usually sit too, just because standing sounds a bit messy. Just make sure if you drip on the seat you clean it off... I hate when I go into a bathroom and people haven't cleaned up after themselves! So gross! But I don't think it's abnormal to stand.