Lots of ways to do this, but just set up a conditional in your templating before calling the built-in Disqus partial and add removecomments: true to your front matter for pieces you don’t want to have comments:
{{if not .Params.removecomments}}
{{ template "_internal/disqus.html" . }}
{{end}}
If chapters is a section…
{{if ne .Section "chapters"}}
{{ template "_internal/disqus.html" . }}
{{end}}