To be perfectly semantically correct (which he was no doubt attempting, as I is a purely visual/appearance tag, and EM connotes some meaning), he should have used
<i> is the correct element, so <i lang="la"> if you wish. A taxonomic designation is the first example given in the specification:
"The i element represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose in a manner indicating a different quality of text, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, transliteration, a thought, or a ship name in Western texts."
<span lang="la">