Surprisingly, out of these 26 papers, only 3 explicitly discuss reasons for patch acceptance or rejection. Rigby and Storey summarized six technical reasons and six non-technical reasons (e.g., project politics) why patches are rejected [12]. Nurolahzade et al. presented five types of reviewer feedback: implementation, functionality and usability, documentation, coding standards, and performance [21]. Rigby et al. examined the Github pull request and manually classified reasons why pull requests are rejected. They found that 27% of the rejected pull requests are due to concurrent modifications of the code in project branches, 16% are due to patch contributors’ misunderstanding of the project direction, 13% are due to implementation errors and 10% are due to project process and quality requirements [22].