I don't know if they've received a penalty or not, and I don't know if anyone would know unless they decided to publicly confirm such a thing. But according to Google, those kinds of links should
be nofollow -- because they're links the authors can place themselves, and frequently tend to be keyword-rich.. In general, the only reason most people are posting to article directories is for "SEO purposes" to start with, which makes them exactly
the kinds of links that Google doesn't want to "count."
So it's also possible they made the change in an attempt to prevent