While the provision of peer feedback has been widely recommended to enhance learning, many students are inexperienced in this area and would benefit from guidance. This study therefore examines the impact of instructions and examples on the quality of feedback provided by students on peer-developed learning resources produced via an online system, RiPPLE. A randomised controlled experiment with 195 students was conducted to investigate the efficacy of the approach. While the treatment group had access to instructions and examples to support their provision of feedback, the control group had no such assistance. Students' feedback comments were coded using an adaptation of the S.P.A.R.K. ("Specific", "Prescriptive", "Actionable", "Referenced", "Kind") model. The results indicate that the instructional guide and examples led to students writing more comprehensive comments. The intervention notably enhanced the presence of feedback traits matching the S.P.A.R.K. model and increased instances where multiple traits of quality were observed in a single comment. However, despite the guide's impact, the students' ability to provide actionable feedback was limited. These findings demonstrate the potential of developing and integrating structured guidance and examples into online peer feedback platforms.