I havent seen him rub on anything, My Longhorn (whom I have named Einstein) nips at him from time to time, but the Lion usually gets his point across. I did treat for what I thought was Ich about 6 weeks or so ago, but no signs that I have any problems now. I will keep an eye out for rubbing, but he hasnt rubbed on anything for the last 8 hours.
I have little experience with Lions, but have been attacked by bateria a couple of times and this doesnt look familiar. Like you mentioned it looks more like an abrasion than anything else and it is uniform on both sides of his body.