You say you were able to access it from above after removing the seat? Wondering if mine would be the same. Our bikes are only a year apart. I remember trying to get at it from behind the tire while it was on a stand. I could not get enough leverage to get it to move either direction. Had a tech at the dealership say the same thing just after I bought it and it had its first service done. I have a super long 1/2" driver extension. Guess I am going to pull my seat and check that out.

 

I can see mine over the drive belt, from the left side. I have recently installed a much bigger starter, which only just goes in, hence reduces accessibility. But I don't recall having any problems when I last tightened my oil filter housing up.

 

Other than on rotating parts where the force of rotation would tend to loosen a bolt, I can't imagine why it would ever be otherwise.

 

It is a normal right hand threaded Bolt and yes you have to remove the starter. I don't see any reason to take off the seat at that point. I also cleaned up the ground and positive connections since they come off with the starter I used some silicone grease on the connections as well as the loctite for the threads.