Apart from the points already mentioned in my three previous posts, quotations may be also a useful device to understand an author's compositional habit and his/her "originality". This concept is in bad need of a definition within Indian standards. In fact, Indian authors may rather be flawed because of plagiarism and are all by and large non-original. Westerners look in vain for treatises about a certain theme and find instead commentaries and commentaries on commentaries, or at most half-commentaries (such as Jayanta Bhaṭṭa's Nyāyamañjarī, which comments only on a selection of Nyāyasūtras).
But, looking at the way one builds texts through quotations and departing from quotations, one eventually understands that an Indian author's skill (and "originality") can be found indeed in his apt arrangement of them. I argued that this is the case of Rāmānujācārya's Tantrarahasya, which is sometimes slightly more than a patchwork of former quotations. Still, Rāmānujācārya manages to collect quotations on the same theme from different works, to put them face to face and to make them, in some selected cases, crash. Similarly, Himal Trikha's PhD dissertation on the jaina Vidyānandin notes how the argumentative steps and the quotations constitute different segments of the text (p.129). That is, Vidyānandin may use several quotation (including loose and unmarked ones) but his structure of the text is independent of them. They are –in Trikha's terminology– Bausteine of his text. This is also proved by the fact that arguments are not quoted en bloc, but rather piecemeal (p.137).
On originality in Indian literature and philosophy, see also In praise of repetition, IIAS Newsletter 2008.