Summary: standard ish. Fixes T4388.
Test Plan: made a comment with L1 and noted L1 linked to L1. Also observed working-ish hovercard.
Reviewers: epriestley
Reviewed By: epriestley
CC: Korvin, epriestley, aran
Maniphest Tasks: T4388
Differential Revision: https://secure.phabricator.com/D8178
