In src blocks, you have the org-block-begin-line face applied. This (in
any sensible theme) has the same background as org-block.

I might be confused by my own config, but that doesn't seem to be the
case. Unless customized, the =org-block-begin-line= inherits from
org-meta-line, and the org-block documentation does specify that it
applies *inside* blocks.

I personaly dislike any inline change of background color. It makes
some sense for the python code, since it isn't org anymore (indeed,
the fontification is done in another buffer), but the src_lang, and
the result part are just org syntax.

Here's an example of a reasonable -- I hope -- use of those faces.

The ~org-src-font-lock-fontify-block~ function could be modified to
take an optional =inline= argument. When =t=, it should not set the
=multiline= font property. Although this is very minor, it would allow
one to easily advice this function to behave differently in inline src
blocks. For example, to not use the =org-block= face in this case.

I don't see where the multiline property is currently set, would you mind
pointing it out to me?

I'm going to be using the original symbols in my configuration anyway
because I think they're nicer, but clearly this is contentious. I'd want
to hear from more people on this.

Since ~prettify-symbols~ seems to be raising some usability concerns,
perhaps ~org-inline-src-prettify-results~ should default to ~nil~.
It'd be unlike org to hide things from the user in the default
configuration.

This seems somewhat sensible to me, but I must say that {{{results()}}}
is /ugly/ and I suspect that many users would like the effect, but a
minority will be aware of this option. Perhaps this is worth doing
anyway.

So are you suggesting I do or don't create new faces for this?

-- 
Sébastien Miquel