Why do post referrals sometimes show a preview and other times not?

[JeeperDon]

Why do some quoted/referred images show a partial image and others posts just show the Subject text above? Post 1732 here is an example of it without the preview. Post 1725 here is an example with the preview. With preview is obviously easier to read. Without preview forces you to click to view to understand the context flow. Is it possible for a code change to always show a preview?

 

[Matrix]

Post 1732 is using attachments, post 1725 is using embedded pictures from other websites. I will see if it can be changed.