Hi, Since when? :o I made a patch for this [1] which I didn't ship exactly for that reason.
We check mtime of theme files but they are preserved when installing updates and so it can happen it doesn't properly nuke it. Also, the Metadata.desktop has a version string but it's always forgotten to bump it when there are svg changes... maybe can be scripted? [1] https://git.reviewboard.kde.org/r/126642/
