Tempo markings render bold and upright; expression markings render italic — and Gradus already gets half of this right

A tempo indication (e.g. Allegro, quarter-note equals 120) is conventionally bold upright roman type; expressive/dynamic-adjacent text markings (dolce, cantabile, rit.) are italic — one of the most consistent typographic conventions across all major engraving authorities.

Gould explicit tempo-vs-expression-text distinction; Ross; Read — all three agree without disagreement, a rare point of unanimous consensus worth flagging as such.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.