Just as a footnote to my last post, Yes and No – footnotes (in MLA8), there is now a post in the MLA’s Style Center which addresses this very question. I don’t think this page was there at the time I wrote my post, but I won’t swear to that.
The question asked was Are notes compatible with MLA style? – and the answer was much as I suggested: in the absence of specific guidance, follow the suggestions made in the previous edition, MLA7: you can use footnotes (or endnotes) to “offer the reader comment, explanation, or information that the text can’t accommodate,” and you can make bibliographic footnotes in limited circumstances: “bibliographic notes are best used only when you need to cite several sources or make evaluative comments on your sources.” Footnotes are the exception, not the rule, not if you want to abide by strict MLA style.
[For the purpose of IB assessments, possibly other exam boards too, you should note that the first use is heavily discouraged: such footnotes MAY NOT be read but WILL count towards the word count.]
Readers might want to know that the latest edition, the MLA Handbook, 8th edition, is now available in Kindle format.