The inline directive generates a form if it has either rootpage, or postform with a "yes-like" value. This means that
[[!inline pages=... rootpage=sandbox postform=no]]
does have a form. I would expect it not to (although mentioning rootpage there is useless).
See also How to disable "Add a new post titled:" submission form?.
My ready/postform-no branch also contains a trivial regression test for
inline. So far the only thing it really tests is that this bug was fixed,
not the actual inlining of pages, but it's a start.
--smcv
this looks simple, straightforward and good to me --chrysn