amanerar

To become mannered, affected, or exaggeratedly stylized — used for acting, speech, or gesture that feels theatrical or self-consciously stylized rather than natural: un actor que amanera sus gestos. Mostly used reflexively, amanerarse.

• El actor amaneró demasiado su forma de hablar en la obra. — The actor made his way of speaking too mannered in the play.
• Con los años, su estilo de pintar se fue amanerando. — Over the years, his painting style became increasingly mannered.
• Prefiere un tono natural y evita amanerarse frente a la cámara. — He prefers a natural tone and avoids being affected in front of the camera.

Confusing amanerarse (to become artificially stylized/theatrical in manner) with the noun modales (manners, etiquette) — they're unrelated despite the shared root, since amanerarse is about affectation, not politeness.