Like I said: Just use Shift-Ctrl-V, if you don't want the formatting. Same in the email editor, BTW.
Bug 1754150 Comment 18 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Like I said: Just use Shift-Ctrl-V, if you don't want the formatting. See "Edit" menu in the standard email editor.