The idea is to make it so that it's very clear to a core dev waiting for review comments to be addressed that the PR is ready for another round of review. Probably something along the lines of when a core dev leaves a "Changes Requested" review that a label is applied like "WIP" and then a comment left for the PR submitter saying that they should send a message to the reviewer like @brettcannon ready for review (changing the title was shot down by Guido at the PyCon US 2017 language summit). That way the reviewer gets a mention notification and the bot can then remove the label. This should lead to the PR showing up in GitHub's notification in a visible way that it's ready for another round of reviews.

I'm not sure if a label signaling another round of review is necessary as the absence of the "WIP" label is a visual signal of that. But perhaps an explicitly "waiting for review" label would also be helpful? This could also be automatically applied to all new PRs to signal when a PR is awaiting an initial review (or an alternative "initial review needed" label?). I also don't know how external reviews play into this, e.g. do we have "need core review" when an external person left a review but a core dev has yet to review?