I've done some more testing this morning and found anomalous behaviour.
Here is the relevant style definition:
node.Test {
defaultCaption: "{name}";
caption: "{caption}";
}
merge (z:Test) on match set z.name='Fred', z.caption='Bill' return z
will correctly display "Bill".
match (z:Test) remove z.caption return z
will (incorrectly, in my view) display nothing. I would have thought given the styling definition, it should have reverted to the "{name}" property.
Similarly,
merge (q:Test {name:'Mary'}) return q
will (incorrectly) display a node with nothing in the text area.
merge (q:Test {name:'Mary'}) on match set q.caption='Karen' return q
Will, however, now add the caption "Karen" to the text area.
This smells like a defect to me.
Paolo