Presumably you upgraded from FP version 10 or earlier.
Yes, this is expected behavior. The output should still be correct.
Further explanation: Due to necessary architectural changes between FP 10 and FP 11, the underlying text editing control will not allow text in the editor to be set in a font that doesn't support the selected characters. Since the barcode font supports only specific characters such as F, A, D, and T, or 0, 1, 2, and 3, to represent the four different kinds of bars, it can't be used to render the name of the data field you're applying it to as a variable. Thus, we have to output a special variable to have the editor mark the variable in that font.
In any case, the output should still render correctly.