So I summoned a Bat with the arguments
{Silent:1,ActiveEffects:[{Id:14,Amplifier:1,Duration:99999,ShowParticles:0}]}
It summoned an invisible Bat like it should. But I could see the potion particles following him when I specifically specified no particles.
I saw a tweet from Dinnerbone saying he changed particles so that they don't hog as much CPU. (Does that mean they are no longer entities?) I assume my problem has to do with the fact that particles no longer operate under the same parameters.
Its ShowParticles:0b.