request for comments on patch re: possible use for 400 status code

Can some folks take a look at the ticket
http://dev.rubyonrails.org/ticket/10328

It is about a possible use for the 400 http status code in restful web
services. There was some back and forth a month ago about the pros
and cons, and I'd like to get some more people's input on it.

Thanks,
Trek