The problem there was the redesign.
You've got a bunch of, not quite AOL-level users, but they're 45-65 and set in their ways. That means the XP and IE6. OK, not quite that bad, but close.
What they should have done was upgrade the tech - sure, use real frameworks. But the full-on AJAX UI "upgrade" was never perceived as an upgrade. Let's look into why:
Problem #1: The highest-ranking feature request since the day it went live has been "to make ignore mean ignore."
Old behavior: I ignore userXXX, I never see anything.
Current behavior: I ignore userXXX, I see exactly the same screen space for a post from userXXX, but it's greyed out. I still have to scroll by it. If I have two trolls arguing with each other or flooding the board with spam, all the content is pushed out of visibility at a rate of 20 posts per page click. The vertical page consists of 80% navigation elements and "Post hidden because you ignored this user."
#2 feature request has been to deal with the spam problem. Now that I can no longer effectively ignore users, I have userXXX1234 spamming for PennyStocksWeekly and in the unlikely event that the spammer's account is terminated, I then have userXXX1235 signing up and spamming about "Penny Stock 101 org" or "Ultimate Stock Alerts."
So Yahoo's filtered out URLs but it has yet to implement even the most trivial Bayesian filtering against these spammers. The exact same text strings are used - but because there's only a URL filter and no Bayesian filtering for obvious spam indicators, there is effectively no spam filtering on the message boards. https://yahoo.uservoice.com/forums/207809-finance-gs/categor... demonstrates the presence of long-term spammers on every board.
And these spammers - see Problem #1 - cannot be ignored; users can ignore the words they use, but must still scroll past the large AJAX/mobile-friendly UI around the string "Post hidden because you ignored this user,"
Old Ignore Infrastructure Fail: There (prior to the big redesign) used to be a silent 1000-user limit (500? I forget what the number was) to the length of the ignore list. When the cap was hit, the user's account was effectively useless, unless the user wanted to manually (!) un-ignore a hundred spammer accounts in order to free up space on this list.
Current Infrastructure Fail: Ignore or message rating or abuse-reporting just doesn't work. First off, the results for https://yahoo.uservoice.com/forums/207809-finance-gs/categor... continue to demonstrate the abuse reporting (and upvote/downvote) mechanism does not work consistently. This has been the case for years.
This data has been available to Yahoo since the big transition: https://yahoo.uservoice.com/forums/207809-finance-gs/filters...
It has been ignored for four years.
It continues to be ignored.
A once-dedicated core of high-value eyeballs has been driven away from the site. Most of them wound up at InvestorHub - http://investorshub.advfn.com/ has a site design straight out of the 90s. To these eyeballs, that was a feature, not a bug. Limits on account creation and posting quantity mostly solved the spam problem. They didn't want to leave; most left only because they realized their feedback to Yahoo was being ignored.
tl;dr: Classic Agilista Fail mechanism. (edit: I apologize to people who are actually being agile, rather than Doing Agile(TM))) The finance message board teams got one or two sprints to make a new UI. They succeeded. The feedback was sufficiently negative and the unresolved issues large (i.e., making the ignore functionality work without breaking some underlying design assumption. Implementing a working spam filter, not just a simple URL filter. Moderators to deal with abuse reports) that they couldn't be done in one sprint.
So none of them got done. And the users left.