Gaining insight into reviewer-author relationships (to avoid causing the chance of a biased review). Twice recently, I think I have basically either invited, or came close to inviting, a person who is now a scientist or academic to review their past PhD advisors more recent paper. Such relationships are hard to find easily as part of the review process, especially in that critical time just prior to when I hit invite.
For example, Google scholar and researchgate has the list of “co-authors” listed alongside anyone there. I wish Scholarone would immediately access that co-author list for all manuscript authors, and then throw a flag if I start to invite/add any review who appears on any co-author list for the manuscript authors. That would help avoid a lot about implicit CoI.
