When "LOI" is used, it actually refers to the Letter of Indemnity. This is standard usage of the term and has been for decades. The Letter of Intent (hereafter referred to as LOI) is often used in specific domestic trades, such as in real estate or corporate mergers, but it has no standard usage in International Trade itself.
Confidential information and agreeing not to use it for competitive purposes: Matters concerning the due diligence investigation are to be treated in confidence and the purchaser will not either directly or through his representatives divulge any such information. The purchaser is also bound not to use the information gained through due diligence investigations in competition with the seller even if the proposed sale falls through.