I added a sentence to the last paragraph of FAQ 44 (How do I buy a paid account for somebody else?), as per technodummy's suggestion in the comments to this post. The last paragraph now reads (new sentence in bold):
Additionally, our bank has informed us that we can no longer accept checks from countries other than the United States and Canada. International users should first try paying by credit card. If this is not possible, or if your credit card is not accepted, you will have to obtain an international money order in United States funds. Depending on your country, you may be able to obtain one of these at a post office.
*hops away, pleased by the ability to edit*