The similarity effect is a phenomenon whereby people tend to be more influenced by others who resemble them in appearance. It has been found to have many positive impacts, including building trust and promoting collaboration performance. While empirical evidence confirmed that similarity effect operates on screen-based communication platforms, it remains unclear how this phenomenon impacts user perceptions and others' persuasiveness in immersive virtual reality (VR) environments. In this study, we adopted a mixed-methods approach to investigating how interaction with avatars of similar appearance to one's own avatar influences conversations. We operationalized similarity as identicality, moderate similarity, and dissimilarity. Avatars of moderate similarity were found to have the greatest persuasiveness; however, in both identicality and moderate similarity conditions, participants felt it was easier to communicate with and lower eeriness rating to avatars than in the dissimilarity condition. We conclude that similarity effect could be leveraged to support persuasiveness in VR-based communication.