Sometimes, websites go 404. Permanent Copy helps with that.
But the bookmark will still miss a thumbnail when the webpage go offline, even if it has a permanent copy.
It's strange that I can have a permanent copy of a whole web page to read from, but the thumbnail will still be missing.
Bookmarks without thumbnails are just harder to recognize.
So it'd be great if bookmark thumbnails were saved as part of Permanent Copy, so that in case the website go offline the bookmark will still have thumbnail which is faster & easier to recognize.