This has been brought to my attention by Emiel van Riel in TWiki:Support/SID-02344
formatting variable contains the wrong value if it refers to a topic in another web.
A short code inspection revealed that the form name is evaluated relatively to the topic where
is used instead of relative to the topic which contains the form.
I tried to whip up a demo at twiki.org which failed because twiki.org runs version 6.0.0, where FORM didn't exist, and the demo here at FormWebDemo
fails with an uninitialized parameter - I guess develop.twiki.org promotes warnings to errors.
Well, the idea can be seen in http://develop.twiki.org/do/viewauth/Sandbox/FormWebDemo?raw=on