I may not have made myself too clear on this one, so I'll try to clarify:

When resolving / closing an issue, the note that follows is probably the most important one for that issue. It may contain text such as "application X no longer accepts decriptions that contain spaces only" or "program Y now includes the option to brew coffe".

These "final" notes should/could be tagged with a release note checkmark, for the purpose of generating a release notes report that can the be distributed with the application or included in the documentation.

This would be a much better "whats new" functionality than that given by i.e vss

We needed some functionality like you describe above also.
And I solved it like this:

• I changed the caption of the "Additional Information" field to "Release Notes" (why this field: because you can use breaks (enter) when entering plain text)
• I changed the output of the changelog page via a custom function to display the content of the release notes field below every solved issue on the changelog page

I think this issue can be fixed:
1) Via a custom field that also allowes breaks (enter) when typing text
2) Via a new field on the advanced page for entering release notes