Take another look at the original sentence:
You wanted to fix it this way:
To delete the comma between Palace and unfortunately would cause an equally bad problem, a fused sentence. A fused sentence occurs when you have two complete sentences joined with no punctuation whatsoever. Susan ducked down ... begins a complete sentence. Unfortunately, a burrito wasn't big enough ... starts the next complete sentence. The spot between Palace and unfortunately needs a stronger break than blank space.
You might want to consult the rules for fixing comma splices and fused sentences.