Reviewers for a journal can sometimes be graduate students or usually postdocs, in addition to professors. For someone in a junior position, such as a postdoc or even an assistant professor, review requests can often be sought after as a sign of professional development and a sign of influence in the field. As a result, they may feel a pressure to provide a good impression to the editors by providing reviews which seem thorough and substantive. A review which may only contain a few sentences, valid or otherwise, may reflect a perceived lack of understanding or effort on the part of the reviewer. Unfortunately, this can lead to a problem of over-reviewing a paper, and lead to an overabundance of suggestions and requested corrections which would obfuscate or weaken the integrity of the paper.
For those with experience in this area how valid is this observation? Do editors view long reviews more favorably over short ones?
P.S. To clarify, ideally, an editor should be the best judge of a good or bad review; however it is understandably difficult for them to easily judge the merit of a paper/review (due to the inherent difficulty of being an expert in every topic covered by a journal, and time) – hence the job of the reviewers.