Hello,

>>>>> Sébastien Vauban writes:

> To select this subtree, I use =C-c @=.

> It does its job, except that it never selects the last line. OK;
> just C-x C-x, add a line, and that's it. Feature? Bug?

Feature. If you want to grab the last line too, use
(org-end-of-subtree nil t)

> Same problem, though more problematic IMHO, with the inline tasks.

> *************** Check how the selection works 
> I'd expect the END line to be selected as well. It's not. 
> *************** END

Here is a suggestion of patch creating a new function org-mark-subtree
(and not using the outline one).

Tell me if it works for you.

Regards,

-- Nicolas