JSHint will throw the "Variables should not be deleted" error when it encounters the delete operator when its operand does not appear to be an object property. In the following example we declare a variable x and then attempt to delete it:
This is the JSHint equivalent of the "Only properties should be deleted" error from JSLint. More detail can be found on the page for the JSLint message.
In JSHint 1.0.0 and above you have the ability to ignore any warning with a special option syntax. The identifier of this warning is W051. This means you can tell JSHint to not issue this warning with the /*jshint -W051 */ directive.