https://hg.mozilla.org/mozilla-central/rev/6151857e7ed8 changed the behavior.
Bug 2006276 Comment 7 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
https://hg.mozilla.org/mozilla-central/rev/6151857e7ed8, which re-landed as https://hg-edge.mozilla.org/mozilla-central/rev/f8c71c831710, changed the behavior.
https://hg.mozilla.org/mozilla-central/rev/6151857e7ed8, which re-landed as https://hg.mozilla.org/mozilla-central/rev/f8c71c831710, changed the behavior.