From the material I have access to here, I cannot give a direct, evidence-based assessment of Leo XIII’s personal or magisterial “stance” specifically on Latin liturgy, because none of the provided documents contain an explicit discussion of liturgical language (Latin vs. vernacular), nor any command/promotion/critique of the Latin rite’s liturgical use. What the sources do support is a broader picture of Leo XIII’s attitude toward obedience, order, and stability of Church discipline—which is relevant, but only indirectly connected to “Latin liturgy.”

What the provided sources do (and don’t) say about Latin liturgy

They do not directly address liturgical language

None of the cited texts in the provided set explicitly mention:

• Latin as the liturgical language,
• the Roman Rite’s usage in particular,
• permissions/restrictions for vernacular in Mass or Office,
• or any reform regarding liturgical language.

For example:

• Est sane molestum (1888) is about correcting certain Catholic periodical authors and urging respect for the sacred obligations of bishops and the authority of documents—not about Mass language.
• The epilogues/closing formulations (e.g., “Nulli ergo…” clauses) appear in multiple papal documents and mainly state that decrees are binding and not to be violated—again, not liturgical-language policy.

So if the question is strictly: “Did Leo XIII favor, oppose, or regulate Latin liturgy?”—I cannot verify an answer from these sources alone.

They do show Leo XIII’s general approach: stability, obedience, and non-violation of Church directives

Several provided texts emphasize that people may not disregard or undermine papal decrees:

• Leo XIII repeatedly insists that no one may violate apostolic letters/decrees, under penalty of divine displeasure and apostolic judgment.
• In Est sane molestum, he reproves authors who depart from Church prescriptions and warns that they cannot presume authority (and that ignoring what Rome hasn’t decided leads to harm).
• In other documents (e.g., Nobis quidem), the tone likewise suggests seriousness about Church matters and the importance of reverent conformity to legitimate authority.

This indirectly supports an inference about “Latin liturgy,” but it’s not proof

Because Leo XIII stresses respect for authoritative prescriptions and does not tolerate open deviation, a reasonable inference is that he would have expected Catholics to remain faithful to the liturgical norms authorized by legitimate authority, rather than treating liturgical language as something individuals can improvise.

However, that inference is not the same thing as “Leo XIII’s stance on Latin liturgy,” and it cannot be presented as a verified position on Latin specifically. It only supports the general claim: he valued stability and obedience in Church discipline.

A careful “assessment” you can make from what’s verifiable here

If you’re trying to evaluate Leo XIII in a disciplined Catholic way (not vibes, not internet claims), the most accurate assessment based on the provided sources is:

• Verified: Leo XIII consistently teaches that authoritative Church directions are binding and must not be violated, especially when people act as though they can override Rome or the lawful hierarchy.
• Inferred (limited): That general posture strongly suggests he would regard authorized liturgical practice—including the Roman norm of using Latin where applicable—not as optional personal preference, but as something to be received and respected.
• Not verified: Any statement like “Leo XIII strongly supported Latin in the Mass/Office” or “Leo XIII opposed vernacular” or “Leo XIII mandated X regarding Latin liturgy.” Those specific claims are not supported by the provided texts, so they would be speculation.

What you’d need to settle this question properly

To answer “Leo XIII’s stance on Latin liturgy” with real certainty, you’d want documents where he addresses:

• liturgical translation or vernacular policy,
• the Roman Rite’s liturgical norms (Latin),
• or responses to controversies about liturgical language.

Those are the kinds of primary sources this answer is missing from the current reference set.

Review questions

1. Which provided documents explicitly mention liturgical language (Latin vs vernacular) in Mass or Office?
2. What do the provided texts actually prove about Leo XIII (obedience/stability vs liturgical language)?
3. What counts as a “verified claim” vs a “limited inference” in Church-historical questions?

Next step (clear and practical)

Send the specific Leo XIII documents you’re using for the Latin-liturgy question (titles or links), or request that you want me to assess particular texts; otherwise, with the current set, the only responsible assessment is about Leo XIII’s general attitude to obeying Church authority, not about Latin liturgy specifically.