Take another look at the original sentence:
You wanted to fix it this way:
To delete the comma between class and under would cause an equally bad problem, a fused sentence. A fused sentence occurs when you have two complete sentences joined with no punctuation whatsoever. For two weeks, Todd refused ... begins the first complete sentence. Under no circumstance would Todd allow ... starts the second complete sentence. The spot between class and under needs a stronger break than blank space.
You might want to consult the rules for fixing comma splices and fused sentences.