1. They were part of their own tradition
2. One agreed with them

By contrast, naming or identifying one’s source was done in order to

• add authority to one’s statements

or

• distantiate oneself from what was said

The synergy of these two aspects leads to the fact that usually sources external to one’s school are identified.

Now, I just read an interesting statement by Vedānta Deśika in this regard. He comments on Pūrva Mīmāṃsā Sūtra 1.1.5, in which Jaimini describes what is śabdapramāṇa and then adds “according to Bādarāyaṇa”. Why this addition?

in order to convey that the whole concept which he (Jaimini) spoke of follows the tradition and is a conclusive opinion (sāmpradāyikatāṃ siddhāntatāñca
jñāpayituṃ).

Even more interesting is the next statement:

In fact, this [mention of Bādarāyana] is not for the sake of highlighting someone else’s view, since what has been said is a valid piece of knowledge (so that one does not need to distantiate oneself from it by saying that it is (just) someone else’s opinion), and since he has not uttered his opinion [as distinct from Bādarāyaṇa’s one] (na hy etat matāntaradyotanārtham, uktasya prāmāṇikatvāt; svamatasyāvacanāc ca).

The implicit consequence seems to be that usually the mention of other sources is used in the case of invalid claims (in order to distantiate oneself from what others incorrectly said) and is followed by one’s own one.

Did you ever encounter similar statements regarding why one names or identify one’s sources? And would you share my initial claim?

I have been working a lot on the topic of textual reuse, especially in philosophical texts. If you are interested, just check the label “reuse” here or “philology” in my previous blog.
Should you really be interested in the topic, you can also read my article about it here and the Journal of Indian Philosophy special issue dedicated to this topic (which should be online by August 2014).