[sciurius]

I guess that's a long grown habit... I'm a guitar player so I have long(er) nails on my right hand. Usually the index finger has the longest nail (a.k.a. built-in plectrum). So my habitual gesture is to use my middle finger for swiping, and the ring finger is then always close, sometimes touching the screen.
Until now it didn't matter but the for the more sensitive screen of the S4 apparently it does...
I will have to adjust my habits. Or wait until you add automatic performance mode .