I haven't discussed this with anyone else but working as an admin it is something that I have noticed over and over again.
In mediawiki the content of a page is easily identifiable using the title of said deleted page. This is not the case in Wikidata however as the title of the page is simply the items ID, eg. Q1234.
Upon deletion of an item it is impossible to know what that item was about unless you, as an admin, go and review the deleted revisions of said item.
It would be great if wikidata stored the labels of deleted items outside of the text body so that once deleted they could still be retreived by Mediawiki and used for redlinks etc.