I've noticed that although it appears one has the ability to sort the favorites folder, by date, c-index and randomly, it defaults to "random" only. I just noticed this today.
No official response as of yet, however +Samatar had this to say, and I quote;
"Not that I know too much about these things, but I imagine the upload date is stored somewhere in the information relating to that image when it is uploaded. Therefore to sort your favourites in the date you added each image the date you favourited each one would have to be stored somewhere in the information relating to the image, and ditto for each other member who favourited the image... could become rather messy after a while."
So, it would appear that whatever changes need to be implemented to allow for sorting of favourites has yet to occur to make full use of that functionality.
Sam, when I do it, the drop down box defaults to "sort randomly" and nothing changes in the folder. It appears as though my favorites are sorted by date, but I am unable to change them via c-index etc. even though the option is there. ;=)