> Hmmm... Aren't you and your friend the "genuine ballad scholar" reading too much into this?

Not at all. The rose *is* a conventional symbol of true love (as in Burns and on greeting cards), and it's hard to imagine what it would be doing in the song otherwise. And briars are indeed thorny and discouraging. Logically the rose should come from the lover's grave and the briar from the jilt's. Versions that confuse the source of the two may be rationalized ad hoc, but they're still confused.

There is no suggestion in the song that the dying and absent-minded lover had either the ability or the desire to "protect" Barbara with his spikes. She seems, moreover, to have needed no protection from anyone.

The point of the rose/briar symbol is simply that the pair are united after death, suggesting the happy ending that heaven is better than the hellhole we're living in now.