What's changed
Payment providers often confirm a payment in several ways at once: from your browser, from their own servers, and through our own check. Occasionally this could set up the same order more than once, adding extra entries to your billing history and sending duplicate confirmation emails and Discord messages. You were only ever charged once.
Each order is now handled by a single request, so its servers, billing entry, confirmation email, Discord message and coupon use each happen exactly once. Plan upgrades have the same protection.