...and shed a great deal of light on Julia's speech, which is extremely important, being the final words spoken in this play, and therefore Sheridan endowed it not only with both poetic beauty, but also with moral and philosophical grandeur. That tells me he must have had a soft spot for Julia as a character, to give her the honor of the last word (other than the Epilogue, of course) delivering these lofty sentiments. The tone is almost Shakespearean, but I have no idea whether (thinking back to the earlier thread about Sheridan's willingness to "borrow" liberally from prior authors including his own mother!) Sheridan was channeling any specific lines of Shakespeare when he wrote that, or if it was 100% Sheridan.

To respond specifically to Robbin's specific questions about that last speech, I too find it warrants close reading to discern exactly what Julia (and perhaps, also, Sheridan) means. Generally, I agree with Robbin generally, and add that the thorns give a sense of the suffering and pain that Julia suffered at Faulkland's foolish hands.