Still trying to understand some audio/video sync issues, I noticed the following weird behaviour (that seems to be related to said issues) of Blender.
Sometimes just opening a .blend file (not modifying anything, and I mean anything) and then exiting (without saving) will cause Blender to silently modify this file, unless it is marked as read-only. Moreover it seems the case that when this happens, the modified .blend file is slightly smaller than the original file (around 3 kB). Also it seems that this 'phenomenon' always occurs when I have these strange audio video sync issues.
Hence I would like to know what causes Blender to silently modify .blend files, and which data it is that is being modified.