Looks like it was a glitch not a feature update
I just clicked a kudo button twice on AO3 by accident because my tablet was lagging, and it resulted in two kudos with my name showing up in the list, rather than one kudo and an error.
But it seems this was just a glitch because of my wonky clicking. At least when I tried leaving kudos again on a WIP I follow that didn't work. Too bad, I wouldn't mind being able to leave more than one, especially with long chaptered stories.