[ripe]

You are right; a good explanation of the rules is in the C FAQ [1], which points to a newsgroup posting by Kaz Kylehu [2].

I am posting the summary here, although please do read the original if you have time:

The most portable thing to do is to use "" for including files within your project, and to use <> only for implementation supplied files.

(Disclosure: I was one of the contributors to the C FAQ).

[1] https://c-faq.com/cpp/inclkinds.html

[2] https://c-faq.com/cpp/inclk.kaz.html