It is my understanding that the trackbar on the front of a YJ helps locate the axle, as without it only the leaf springs keep the axle centered which would be fine if not for the shackles being in front. This is why it is ok to remove the rear but not the front.
I was told, and I think it good advice, that if you want to remove the front trackbar on a YJ, then do a shackle reversal first.
If you have a shackle reversal you can run a YJ with no trackbars or swaybars.
I will have to add that when I ran my YJ with no swaybar, it was a little hairy at highway speeds in high winds. That prompted me to put it back on that very day. I decided that disconnects were the better way to go for me. Just something to keep in mind.