In immersive virtual reality (VR) environments, experiences of harassment can be exacerbated by features such as synchronous voice chat, heightened feelings of presence and embodiment, and avatar movements that can feel like violations of personal space (such as simulated touching or grabbing). Simultaneously, efforts to govern these developing spaces are made more complex by the distributed landscape of virtual reality applications and the dynamic nature of local community norms. To better understand this nascent social and psychological environment, we interviewed VR users (n=25) about their experiences with harassment, abuse, and discomfort in social VR. We find that users’ definitions of what constitutes online harassment are subjective and highly personal, which poses significant challenges for the enforcement of platform- or application-level policies. We also find that embodiment and presence in VR spaces make harassment feel more intense, while ephemerality and non-standardized application controls make it difficult to escape or report unwanted behavior. Finally, we find that shared norms for appropriate behavior in social VR are still emergent, and that users distinguish between newcomers who unknowingly violate expectations for appropriate behavior and those users who aim to cause intentional harm. We draw from social norms theory to help explain why norm formation is particularly challenging in virtual reality environments, and we discuss the implications of our findings for the top-down governance of online communities by platforms. We conclude by recommending alternative strategies for community governance.