I'm not sure how a lender would view it, but I think the fact that the OP is paying it is enough. His friend's credit practices shouldn't reflect badly on him. The fact that OP is willing to actually pay off somebody else's debt is actually a huge positive in my eyes. Who knows, some credit analyst might think that your friends' habits rub off on you.
The cosigner part makes you equally responsible for the debt right, like a joint account?
If that's the case, you should call them and see if you can get them to report the positive history on your CRs.
If the original debtor included this account in the BK though, you might want to think about maybe letting this account be. I'm not sure if they would notate that on your report, which would probably look really, really bad on a manual review.