Several months ago I posted about VLC Portable leaving stuff in &APPDATA and IIRC the post was ignored, which I took to mean "we can't reproduce it" or "we don't know what to do about it". (Silence is possibly the mother of assumption.)
I have an idea that might lead to a solution or at least an explanation.
How do the PortableApps launchers handle %APPDATA if it's on a volume other than C? Windows is on C on this particular computer but the users' profiles are all on D, which is on the same physical drive as C, it's just partitioned. I have no idea why they did it this way. I do know the computer gets its updates not from Windows Update but some corporate thing I've never seen.
Maybe the launcher is seeing no %APPDATA on C and is just ignoring it, yet VLC itself is writing to %APPDATA and leaving information behind. It isn't personal information, but it can be sensitive information. While I don't believe anybody should be watching DVDs (it records the DVD volume name) they'd mind their boss watching with them at work or their teacher at school, I do believe it falls under the definition of portable to clean up.