Here's why:
* Appositives: The phrase "the home of Thomas Edison, inventor" is an appositive, which means it renames or clarifies the noun "Milan, Ohio". Appositives are usually set off with commas.
* Clarity: The comma helps the reader understand the sentence structure and avoid confusion about what is being described.
Here is the corrected sentence:
"The tour bus stopped in Milan, Ohio, the home of Thomas Edison, inventor."