Gil-Hwan:
I think I've found why this is happening. Bear with me. I'm going to explain it in technical terms, so if it's confusing, just skip over the technical part.
ETP calls a proc called util_close_html_tags to make sure that the HTML people type in is legitimate. One of the side effects of this proc is that it REMOVES all FORM tags. That's actually the only tag it removes.
The only reason I can think of for doing this is security. It can be a security problem to allow people to post FORMs in your website.
However, if you're willing to take that risk, you could edit
packages/acs-tcl/tcl/text-html-procs.tcl
and change this line:
set syn(FORM) discard
to
set syn(FORM) close
I think that should work.
