I have given this a bit more thought...even if IRS holds the PERSON liable for some income tax, can't you request a discharge of the debt per 12 U.S.C. 95(a) if they send you a bill? I suppose if there were any withholdings they would subtract that out of any refund.

I see plenty of merit in the argument of just letting it go. But if one were so inclined, one could request a refund making the argument that one did not knowingly agree to be an accommodation party; and one could sue after 6 months if IRS won't honor the refund claim. I think it would be a fact matter for a jury to decide as to whether a reasonable person would know he was agreeing to be an accommodation party by simply signing the back of his paycheck to get paid. It might be interesting to see if they would let things get that far...

On the other hand, if there is no refund claim to be made, and it is just a matter of them sending you a bill, one could attempt to discharge it, or ask them to declare the amount not collectible (this can be done when there is some doubt as to whether the amount is owed) or compromise on the amount on that basis. The libel of review might discourage them from collecting as well.