I just switched to a different comments editing plugin today, with help from CGP in Scotland to test and make sure it worked for her. The new plugin doesn’t use AJAX, which I think was the source of the problem. What that means basically is that when you edit your comment the whole page refreshes, just as it does when you leave a comment for the first time, and similarly that you have to refresh the page to see how much time remains in which to edit.
I do have the new Safari for PCs, and it seems fine. Initially, it made the fonts fat and ugly the way IE does on an old-fashioned monitor like mine, but then I discovered how to adjust that, and now it looks as good as Firefox or Opera. I didn’t test it for comparative speed. I am having some trouble with this theme not displaying properly in IE and Opera, for example by not centering the footer under the main column, but Safari shows the same as what I see in FF.