Hello
I like Dan's idea and it's simple. A brightness / flash could give the button visibility enough for people to see. I believe that many people do not see the button to accept an answer.
I will not vote during this month to get information and help with this problem.
It is difficult to find solutions to this without "forcing" the OP. adding mandatory or more specific fields. For this reason I would try visual methods as Dan says. I can't think of anything else that doesn't involve more "effort" for the OP.
