Doing all nodes smooth was exactly the change Peter made about 3 weeks ago. Before that, most if not all nodes were sharp, now they are all smooth. However, making them all symmetric as well as smooth would be an overkill I think. A symmetric node implies that the curvature before and after the point is constant, which is rearely the case.
Bulia, have you or Peter tried making them them all symmetric? It may not be 'overkill' since although 'the curvature before and after the point (node) is constant', the final drawn curve that actually runs through the node is not a mirror image because the curve is also affected by the nodes on the opposite end of each adjacent curve segment.
Admittedly we haven't tried symmetric nodes yet. If Peter can code this I would be interested to compare.