Written feedback commentary (WFC) on L2 student writing is a widespread and time-intensive teacher practice, serving a range of roles and purposes. One of the challenges in providing effective WFC is attending to the many content and delivery options that are possible, some of which have been shown to exert tangible effects on students and their texts. This article presents a typology of characteristics of teachers' written comments, synthesised from 30 years of empirical research. Ten strategies for providing WFC (focus or target, mode and tone, syntactic structure, text specificity, location, explicitness, length, presence of mitigation strategies, pen-and-paper versus computer-mediated delivery, and temporality) are outlined. Thereafter, the paper presents the available options relating to student response to written feedback commentary. Each characteristic is illustrated and research into its effectiveness reviewed.