I am the lucky owner of James Felici’s magnum opus The Complete Manual of Typography (second edition). In most documents I write (academic), I prefer using EB Garamond, as it now is a fully-fledged font with support for most symbols, as well as excellent Greek. I recently discovered that in subset 1 of the font, there are petites. I cannot, however, find any instructions on neither when nor how petites should be used in Felici, and I do not have access to any other such books at my library.
There is a somewhat related post about this topic here, but it does not say anything about the usage of petites (only small caps).
- Here is the font instruction I use in my regular text when enabling ss01 (in LibreOffice):
EB Garamond:liga=1&calt=1&onum=1&pnum=1&ss01
- Adobe’s list of OpenType features: ‘Syntax for OpenType features in CSS’
It seems strange that this alternative would exist without having a prescribed suggestion for how to use it. Is it, for instance, better suited to running text (e.g. on the first line after an initial?), whereas small caps should be used for shorter segments (acronyms, abbreviations and the likes)? I just don't have any idea, but expect there to be a typographic consensus as to what is the better usage.