Below is a link to a blog post entitled "There is no black and white definition of predatory publishing" by Kyle Siler for the London School of Economics blog, May 13th, 2020 with a short excerpt.
Siler argues that journals are criticized for a wide range of problems and bad practices ranging from lacking an editorial board entirely or using a fake address to relatively minor offences such as having dead links on their website or including bad grammar in articles.
He comments that:
"The role played by peer review is key to this issue. Despite being essential to the quality of a journal, peer review is often an opaque activity, with the journal brand acting as a signal of quality and trustworthiness. Complicating matters, some predatory journals appear to conduct some sort of peer review, while others do not. There is also confusion around the different standards of peer review applied by large-scale open access publishers. One means solving this issue would be the wider application of open peer review as a way of demonstrating the quality of peer review and exposing poor practice."