Using sourceRectAtTime expression to recreate comments section

You can use sourceRectAtTime() to calculate the height of a text layer. Add inPoint to the end and some padding, and you can easily make a layer jump up when another layer starts. All you need is an expression on the text layer's position property. If you throw in an if statement and interpolate the movement, and put the expression on all but the bottom layer, you can get something like this:

Here's the expression:

ref = thisComp.layer(index + 1);
refH = ref.sourceRectAtTime().height;
refP = ref.position;
y = refP[1] - refH - 20;// 20 is the padding between layers
x = refP[0];
m = .3; // move time in seconds
t = time - ref.inPoint + m;
if (time <= ref.inPoint - m){
	refP;
}
else{
	y = ease(t, 0, m, refP[1], y);
	[x, y];
}