This is a dupe of 1537885, now fixed in Firefox 68. Is this still reproducible for you?
Bug 1539827 Comment 5 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
This is a dupe of 1537885, now fixed in Firefox 68. Is this still reproducible for you? Tested on the latest Nightly build and couldn't reproduce the issue following the steps from description and comment 2.
Thanks for the report! Tested on the latest Nightly build and I was able to reproduce the issue following the steps from description and comment 2.