The link classification change has nothing to do with Panda. Google announced something like 40 algo updates recently. One of them was a change in the factors they use for evaluating links. Another one was a Panda update. The two are not related. (Panda relates to content, not links.)
As to the link change, about all we know is that there is some factor they used to consider, but lately they decided it isn't as useful as it once was, so they stopped using it.
Google is not giving out any further information about what, specifically, was changed. I wouldn't expect them to, given the weight that links in general seem to carry in their algorithm. They don't hate SEOs, but they aren't going to hand us the secrets to their algorithm on a silver platter, either.
There's a lot of speculation out there among the algo-chasers as to what exactly might have changed. Read it if it interests you, but keep in mind: no matter how certain
any of them sound, no matter how authoritatively they write, they're all just guessing. Some guesses are more educated than others, and it's possible that some of the guesses may be close to correct, but in the final analysis, they're all sheer speculation.
Nobody outside the Googleplex knows for sure
what changed. And nobody inside
the Googleplex is going to say.
Best thing to do is to continue to The Right Thing. Seek links that will send you good actual human traffic, give links to valuable resources your visitors will find useful.
, adjusted for inflation.