Yesterday Microsoft released an cumulative update for SharePoint 2013. This update fixes the issue with version comments that are not saved in SharePoint 2013. See my previous post: Version comments not saved in SharePoint 2013
Text from Microsoft (to reproduce):
Consider the following scenario:
- You create a SharePoint Server 2013 document library that has the Versioning and Required Check Out features enabled.
- You upload a document to the document library.
- You check in the document and then leave a version comment.
- You check the version history of the document.
In this situation, the version comment is blank.
Cumulative update for SharePoint 2013: KB2825647