Thank you for your support!
For anyone else that has this issue, I also had to perform the following steps to get everything working properly:
- Add cpage as a global non-SEF variable in JoomSEF settings
- In JoomSEF extension manager, set JomComment to use default Joomla SEF router
- In JoomSEF click 'Manage SEF URLs' and do a search on the real url for any which include cpage. Delete all filtered to remove any stale Jomcomment variables.
- Delete both JoomSEF cache and Joomla cache. Not sure if this step is necessary
After performing the above, and editing the code per david's post, JoomSEF and JomComment work very nicely with each other. Thanks again!