Thats unfortunate. I always think its easier to tell genuine autos in ballpoint over felt tip. The Bon Scott looks completley natural, and has the right 'feel'. Have been looking for a good Bon Scott myself. I know I will get a good one at the right price eventually. I enjoy the search.
I've got allot of AC/DC signed memorabilia but I would still have to admit that I'm certainly no expert so take my opinion with a grain of salt. I think these are authentic.