Steve, they're not complete idiots at Yahoo, they're only half-wits. They only killed off half the links to the message boards, the ones from the stock summaries. They left a few others around.
You can still get there by using the search box on whatever board you are on. Set it to "All Yahoo message boards." Put in your ticker symbol of choice, CNE or whatever. Search away, the link to your chosen board will come up. See you at the CNE board.
As to contacting Yahoo, I tried e-mailing them off their feedback links, but there's never any response. You might just as well try e-mailing the Playboy Playmate of the Year for a dinner date.
Obviously, Yahoo is devoting its energy to catching up to its biggest competitor. Given their limited corporate cognitive abilities (like how long has "Canetic Energy" message board been called "Career Engine Network" Duh?), I hear that they're looking for someone called "MacDougal" and they've dispatched a crew of Yahoooligans to lower Manhattan to find him.