Almost every method in the Quaternion class (from) return this.
This allows for code like

Quaternion q = new Quaternion().fromAngles(0f, FastMath.PI, 0f);

Quaternion.lookAt() doesn't yet, so the code would look like

Quaternion q = new Quaternion();
q.lookAt(v, Vector3f.UNIT_Y)

Which especially in a case where you'd just want to pass a lookAt to a method, makes your code look worse. It's also not consistent with the other code (lookAt even uses fromAxes, which returns this), but looking at it's position in the file, it has been added later and just overlooked this convention.

Also changing this wouldn't break any user-code.

What do you think?