The release notes for Fresh releases are quite general and the release notes for the stable release have all the things that changed since the last stable version.
How do I find out what exactly changed from one Fresh release to the next?
You just have to go one level up (and find yourself in a not-so-friendly page)
https://wiki.documentfoundation.org/ReleaseNotes
The English notes are the ones without any language reference. Translations are indicated by the last two letters e.g. Neuerungen und Veränderungen in LibreOffice 4.1 - The Document Foundation Wiki are the notes in de = Deutsch = German
If you want the fine details between each third level release (and each RC, Beta, Alpha, etc) you will need to read these
https://wiki.documentfoundation.org/Releases
Those are the updated release notes for the major release number (4.2) but I would like to know what changed between 4.2.3 and 4.2.4…
@karolus, bug fixes ARE important changes from a user perspective! Minor releases only means that no features are added 