OK, I'm an idiot. I just did find a use of -1 for a $depth variable in a MODX add-on -- IN MY OWN CODE.
It was not in a property, though, but in an argument to a recursive private function, so I can still say I've never seen one in a property.
Also, looking back on my earlier posts in this thread, I didn't mean them to sound so proscriptive. MODX is, after all, about creative freedom.
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PLEASE, PLEASE specify the version of MODX you are using.
MODX info for everyone:
http://bobsguides.com/modx.html
