some confusion on field binding

[Michael Allman]

There seems to be a facility in the BeanAdapter.get method for getting the 
value of a field from the underlying object.  The block I'm referring to 
begins

        if (key.startsWith(FIELD_PREFIX)) {
and is in Pivot 1.5.  But when I try to use this by setting a textKey 
attribute to a field name prefixed with a ~, I get an

JavaException: java.lang.IllegalArgumentException: Illegal identifier 
character.

What's up?

Cheers,

Michael