The MLI, essentially by virtue of being applied in a global manner, lends itself to English and French being the only authentic texts

A group of 14 lawyers from around the world gave somewhat presciently, before the release of the Multilateral Instrument, the rationale for it to not operate by way of modifying existing bilateral tax treaties but, instead, to modifying bilateral tax treaties between the MLI signatories without specifying them individually, so that one would resort to the MLI for the relevant wording. What in fact happened was something along the suggested lines, but with optionality where a minimum standard was not involved, so that individual articles would be specified, and with the covered Treaties also specified.

In the course of discussing this broader issue, they noted that around 90% of treaties have an authentic English or French version – and respecting the countries which have concluded tax treaties in neither English nor French, “there are some pointers to the likely result” that they should largely be content to have the MLI be implemented in English and French only. This comment also was prescient - the MLI provides that the authentic languages are English and French only, so that where questions of interpretation arise in relation to "Covered Tax Agreements" concluded in other languages or in relation to translations of the MLI into other languages, it may be necessary to refer back to the English or French authentic texts.

Neal Armstrong. Summary of Stéphane Austry, John Avery Jones, Philip Baker, Peter Blessing, Robert Danon, Shefali Goradia, Koichi Inoue, Jürgen Lüdicke, Guglielmo Maisto, Toshio Miyatake, Angelo Nikolakakis, Kees van Raad, Richard Vann and Bertil Wiman, “The Proposed OECD Multilateral Instrument Amending Tax Treaties,” Bulletin for International Taxation, December 2016, p. 683 under Treaties.