shouldComponentUpdate clauses should be flattened.

[shammamah-zz]

No obligation here but would suggest flattening this for readability.
Same comment applies to other shouldComponentUpdate.

shouldComponentUpdate(nextProps) {
    if (this.props.modelData !== nextProps.modelData) {
        return true;
    }

    // if one is defined but not the other (XOR)
    if (this.props.selectedAtomIds ? !nextProps.selectedAtomIds : nextProps.selectedAtomIds) {
        return true;
    }

    // etc.
}

Originally posted by @Marc-Andre-Rivet in #411