Hi Christian, okay, I reverted my wrong fixes. I'll let Nicolas have a look.
I would not favor a solution that allows more #+begin_ blocks to be inlined. The proper way to handle this is to introduce a new syntax for inlined annotations and to treat them appropriately in exporters. Since we have both #+begin_src and src_<lang>{...} I'd suggest having annotation_{...} or something similar. The LaTeX exporter could use \marginpar{...} and the HTML back-end could make them appear when hovering with the mouse on the annotated parts (just an idea.) Maybe we will have to live with the current "regression" for 8.0 and implement the new syntax for 8.1. Or for 8.0, if Nicolas thinks the change is okay and not too error prone. Best, -- Bastien