Ups, seems like there was a typo in the reviewing guide - thanks for
noting!
You can communicate with the authors using the HotCRP website. When
you are on the dashboard of a given paper (for example
https://systemsandml20ae.hotcrp.com/paper/1), use "Add comment" on
the bottom of this page. Your comments will be sent to the authors
via email and they can reply on the same dashboard - you will be
immediately notified by email too.
It's a convenient way to keep track of the communication between the
authors and the evaluators. We also take it into account when
assigning the reproducibility badges.
Cheers,
Grigori