Open the Comments Panel, click the Options button in the Comments List section and select Create Comments Summary.
I see. That would require using a script.
I've already developed a script that can export the comments summary to a text file (Custom-made Adobe Scripts: Acrobat - Create Comments Summary (TXT/PDF) ), so adjusting it a bit to create a CSV file that can be opened in Excel should not be a problem.
Feel free to contact me privately via try6767 at gmail.com to discuss it further.