This paper explores the morpho-semantic properties of degree constructions in Ersu, a Tibeto-Burman language, with a focus on the morpheme ya-. The study examines the use of ya- in positive and negative adjectives and explores its interaction with morphological markedness and semantic interpretations. The paper demonstrates that, in addition to fulfilling an anti-monosyllabic constraint on DegPs, the use of ya- may also give rise to an evaluative reading in certain degree constructions. Furthermore, it is shown that evaluativity arises in slightly different ways in positive- and negative-antonym constructions in the language. The findings contribute to the broader discussions on evaluativity and its interaction with morphological markedness.