Our dear St. Beatus of Liebana, who has hitherto been quoting mostly the Fathers and the Scriptures, has apparently decided to branch out more in his reading as he approaches the last fourth of his Commentary on the Apocalypse.
He is throwing in the odd quote from Virgil and Seneca. Quotes that nooooooobody else caught, and which I am only catching because you look at them, and you look where you’ve marked the quotes with colored marker and where the page is unmarked, and you see there are unmarked bits that look like quotes, and you run them through the search engine and they are.
He is also cramming more subtle Bible quotes into his sentences, and the critical editions haven’t been catching that, either.
It is very nifty, but it is also very scary to be the only one noticing this stuff. And what if he’s quoting lost sources? There are some bits that definitely seem like quotes but don’t produce any search results.
On the bright side, computational linguistic analysis of texts is getting more sophisticated.