The length of comments provided in five of the 19 studies, arranged in descending order according to the total number of comments
| Author | Data source | No. of comments | Length of comments |
| Hao et al51 | Haodf | 773 279 | Mean 95.75 characters |
| Rastegar-Mojarad et al57 | Yelp | 79 173 | Median 635 characters |
| Wallace et al32 | RateMDs | 58 100 | Median 41 words |
| Wagland et al48 | Cancer survey | 5636 | 1–225 words |
| Plaza-del-Arco et al58 | Masquemedicos | 734 | Mean 44 words |