Mixed research findings on peer feedback indicate that its efficiency seems to be influenced by its characteristics, its mindful cognitive processing, and the presence of justifications. Further, these aspects seem to positively or negatively affect cognitive load in the recipient. In a 2 x 3 design, we systematically varied types of peer feedback (elaborated specific feedback with/without justifications) on an essay and sender's competence (high/ average/low). We measured cognitive load during the peer-feedback reading and performance tasks and correlated eye tracking data with performance measures to infer mindful cognitive processing. We found an interaction effect of justifications and sender's competence on text-revision performance. The impact of justifications on text-revision performance was moderated by cognitive load. Mindful cognitive processing seemed to increase when more transitions between text elements occurred, however, more intense mindful cognitive processing did not necessarily lead to better performance but rather served a compensatory purpose to sustain performance.