The way SMF is right now, yes. >_> It's partly security, partly the well-orderedness of the site. On the wiki, if you mess up someone's page they can just go back and fix it. Here you'd have to beg the poster above you - or a staff member - to fix a broken tag. We have enough of those problems with hotlinked images, as is. The alternative is to encourage absolutely atrocious, tedious coding.
Anything too complex belongs in the new CMS, regardless : )