SQLite3: multiple self join

I have a table in my DB which holds all the words in a text along with some information about their font and position. I am trying to get a view which contains the lines of my text and until yesterday I simply used a GROUP BY y clause, in which y is the height of the word. Today I was told to add support for OCR-recognized texts, so I need to allow for a certain degree of freedom in the clause and the GROUP BY y doesn't do what I need anymore.

My first attempt was to switch to move the check inside a WHERE y1 - y2 <= some_range clause, or something similar, but the point is, I don't know how may words a row holds. Is there a way to manage n self joins in SQLite 3 or do I need to extract the data, perform some number magic inside my application and then insert them again in my DB?