For better or for worse (I'd argue worse from an accessibility perspective), Firefox's behaviour was changed to conform with other browsers several years ago as part of the work on e10s.
Bug 126379 Comment 177 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
For better or for worse (I'd argue worse from an accessibility perspective), Firefox's behaviour was changed to conform with other browsers several years ago as part of the work on e10s. See bug 1350700.