I just read the preamble discussion regarding guaranteed payments for the use of capital that you pointed to.  I agree that it is interesting.  The key sentence in the preamble is, "The Treasury Department and the IRS believe that guaranteed payments for the use of capital are not attributable to the trade or business of the partnership because they are determined without regard to the partnership’s income."  I assume that what IRS means by that is that guaranteed payments are a legal obligation that exists regardless of the income  of the business, since that is the definition of a "guaranteed payment."  Other deductions (including charitable) would not, in my opinion, fall within this exclusion.  The amount of those deductions is dependent on the income of the business, as the partnership would not incur the expense if it did not have the income to do so.