Disagree:
A corner grounded delta is exactly what the name says, a delta secondary where one of the terminals is grounded. Since each terminal of a delta has two transformers connected to it, this means that _two_ transformer secondary terminals are connected to ground. Any conductor connecting to that terminal is a _grounded conductor_ and should be coded white.
The grounded conductor carries full current, and if opened presents the same sort of risk as when opening any neutral carrying current. I guess in ideal operating conditions a neutral would carry zero current, while a corner grounded conductor would carry full phase current, so the risks are different, but IMHO this is no more of a risk than a three wire feed (including the 'neutral') from a 'wye' secondary, which also carries full current if the two phase conductors are balanced.
The grounded conductor in general should not be opened, although it is permissible to open the grounded conductor with suitable switches/breakers that open both grounded and ungrounded conductors at the same time.
I suppose that one could have a 'corner' grounded open delta, or even a 'corner' grounded wye secondary (the latter being an explicit code violation since the selection of the grounding terminal is supposed to be one that minimizes the voltage to ground of the other terminals). I don't see these are any riskier or safer than any other grounded conductor.
-Jon
