Hi Sam,
The search scopes are used for excluding items which meets the conditions from search results.
To exclude the Check In Comments column from search results, I recommend to set the NoCrawl to True for the Check In Comments column programmatically or using SharePoint Manager.

More reference:
https://msdn.microsoft.com/en-us/library/office/microsoft.sharepoint.spfield.nocrawl(v=office.14).aspx
Best regards,
Victoria
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