We consider an electronic analog of the Hong-Ou-Mandel (HOM) interferometer, where two single
electrons travel along opposite chiral edge states and collide at a Quantum Point Contact. Studying
the current noise, we show that because of interactions between co-propagating edge states, the
degree of indistinguishability between the two electron wavepackets is dramatically reduced, leading
to reduced contrast for the HOM signal. This decoherence phenomenon strongly depends on the
energy resolution of the packets. Insofar as interactions cause charge fractionalization, we show that
charge and neutral modes interfere with each other, leading to satellite dips or peaks in the current
noise. Our calculations explain recent experimental results where an electronic HOM signal with
reduced contrast was observed.