Ah yes, I see that now. Thanks!
I guess it looks less cartoony, but I'm not sure if it impacts on the feel of the strips. It might make colouring a bit more tricky!
Back when I was studying art we were always encouraged to not use outlines at all, edges were defined by tone and colour, but that just doesn't work with comics, where there is rarely enough time to add sufficient detail to generate that type of contrast to the edges. Maybe it's a sign of Jeph's increasing confidence in his artwork that he's using thinner lines, and maybe one day they will disappear altogether... Or not.