I modified the -html_p parameter to forum::message::new, renaming it -format. There are no traces of html_p left anywhere that matters (I'm on Oracle):
[janine@pacad2 forums]$ fgrep -rl html_p *
However, every time I restart the server, it reverts back to thinking that the parameter is called -html_p, and when I call it with -format I get an error. I turn on watching for the forums package and go into tcl/messages-post.tcl and add a comment to the ::new function. Voila, everything works again until the next restart, even if I remove the comment.
I've even verified that it thinks I should be using -html_p by changing the name back in message-post.tcl and verifying that the error goes away. This is truly bizarre.