Evidence occupies a paramount position in any logical endeavor and research article is consensually considered a predominant site of such an endeavor. One interesting area of rhetoric which addresses the source and reliability of evidence is quality metadiscourse. In this qualitative study, quality metadiscourse strategies (i.e., evidentials, hedges, boosters and disclaimers) are examined to investigate their contribution to evidentiality in research articles. Through analyzing authentic examples taken from research articles, it is concluded that evidentials mark the source of evidence and the other strategies are employed to condition propositions proportionate to the strength of relevant evidence. In fact, this study helps to argue that reliability markers demonstrate the author-perceived distance of propositions from the impact range of evidence. Contrary to the broad definition of metadiscourse, the paper concludes that without appropriate types of markers, propositions could lose their quality, and as such, they are an indispensable part of the propositions they modify in the broader pragmatic context. Thus, in addition to a contribution to the definition of metadiscourse, this conceptualization is hoped to facilitate teaching and learning quality metadiscourse in that it defines a more plausible base to the appropriate employment of quality-related metadiscourse strategies.