Is is ever appropriate or acceptable to debit Revenue when recording an allowance for doubtful accounts? Or do you have to debit Bad Debt Expense? FAS-5 doesn't seem to address this from what I can tell.

Your right FAS 5 doesn't address this. However it is common practice not to debt revenue but as you mentioned some kind of Bad Debt Expense account.

That might be in a later FAS but don't know it off the top of my head. I just know for sure you don't debt revenue but you do debt expense.

If you think long enough about it I am sure you will come up with several reasons it isn't right to debt directly revenue.