The use of reflective interfaces has been proposed as a useful strategy to reduce cyber harassment amongst adolescents on social networking sites (SNS). By using machine-learning techniques, harassing online messages can be detected before a user submits it online, whereafter a message prompts the user to reconsider the post. This study builds further upon research focusing on the short-term effectiveness of reflective interfaces in preventing harassment. In this context, though, it is not unlikely that adolescents' user experience with SNS is thwarted when it contains reflective interfaces that might steer their online behaviour. Therefore, this study explores how adolescents evaluate a reflective interface design, in terms of both pragmatic (i.e. functionality, clarity and supportiveness) and hedonic qualities (i.e. autonomy, privacy, self-expression, self-reflection, and pleasure). Moreover, experienced emotions were investigated. In a mixed-method experiment, 24 adolescents (aged 14-16) interacted with a mock SNS with reflective design features. Participants' emotions were observed while interacting on the SNS that prompted a cue (either containing a verbal message or implicit) for each textual harassment attempt. We further investigated the participants' experiences retrospectively while watching the screen capture video of their interaction with the reflective interface, and administered a self-report questionnaire. Findings reveal that adolescents' short-term experiences with SNS in which reflective cues are implemented are not disrupted to a high extent and attitudes are rather positive. Nevertheless, results clearly pointed to a potential fatigue effect in the long-term. Methods to overcome this and alternative options for providing reflective interfaces are suggested.