[twentyafterfour] Obvious to me: Move to Phabricator. Phab has Owners tool. Call to action: Set up an owners package for stuff you care about.
Task: Document the Owners tool in Phabricator (or link to sufficient documentation) on https://www.mediawiki.org/wiki/Phabricator/Differential and once done, advertise using it.
Owners allows assigning reviewers based on file ownership so reviewers get notified of patches in their areas of interest. (Limited equivalent in Gerrit).
Intention: This might help improving the situation described in https://www.mediawiki.org/wiki/User:AKlapper_%28WMF%29/Code_Review#Workload_of_existing_reviewers