@jkeyser1 ...
That seems very strange that replies from discussion topics copied over into your new course. Normally, only the discussion topics themselves would copy over...not any of the replies from students in the past course...mainly because students in the past course aren't normally in the new course...and you'd want to start off with fresh conversations anyway. Can you try and clear your browser cache, close your browser, and then re-start your browser to see if the replies are still showing up in your Summer 23 course?
If that doesn't help, I think you might need to reach out to Canvas Support to see if they have any other thoughts/insights for you.
How do I get help with Canvas as an instructor?
Please keep us posted...thanks!