I might be wrong, but from that video and looking into the example sites, it does look to me like a glorified forum, only meandering around with no clear target but lots of opinion. It may be a better interface than the garden variety of forums, still nothing I would be inclined to spend time with.
More important might be the fact that those Discussions are implemented as a distinct, not integrated, feature. The same problem as with the existing Chat. If not more as it's based on the same premise as the main site: Putting up a question.
Having to decide if something is a question looking for answers or a Discussion calling for opinion might be already hard knowing the tool, impossible for most. Using the 'wrong' type will be common, degrading usability to either. Not to mention 'crossposting' of the same topic twice with slightly twisted wording.
Some (not me) still believe we need to work harder to acquire more questions, no matter how bad. Splitting this in two will not improve anything.
The idea of having two parallel columns might be doable in a close knit community or within a company setting (which SE might target for).
The main issue with chat is its non integration. A simple link about comments being moved does not bring any additional value or insight - and is almost never creating an urge to look. To do so it would need a way to tease about what is discussed there.
Bottom line: it's not working and I see no way for better integration.
Regarding the cited comments:
Yes, discussion does often include quite valuable additional information - but as often it's about some romantic memory (I'm quite guilty of that) or lingering away into pointless what-if-the-dog-hadn't-taken-a-nap style assumptions.
I do not see how the existing pearls can be better highlighted than already done by upvoting comments. Maybe adding some kind of 'qualified' vote? No idea.
Also, there's a huge difference between comments and a discussion: the former is present on questions AND answers and used differently for either:
Below a question it serves to improve it, request additional information and deliver small hints that may not qualify as answer (or when not enough time to do a full answer)
With answers they are used to add additional viewpoints, information and related stories - as well as ways to improve it.
A generic discussion can not replace, not even enhance it.
What I Could Imagine:
At first I thought it might be a good idea to have a prominent link for starting a discussion right below any question and maybe a box with links to the last 2-3 entries, but then again, those may be exactly the content which otherwise would have made me ignoring it in the first place :(
Then again this question made me think about a possible use by being able to move such rather off topic questions over to a discussion format.
The idea would be that discussions would not be part of regular RC.SE usage as in no user may open a discussion, but qualified voting may turn a question into a discussion, which from that point on is free form.
Walter Mitty's answer shows perfectly how such an off question does attract interesting reply without getting really answered. Which I would think is what the whole idea of using discussions to preserve worthy information without polluting comments and answers is about.
Them being discussions instead of questions will clean the main Q&A section while still allowing to pursue the idea.
On the backside this may quite often collide with transferring the question to another site where it may be better suited.
Important Fact to Remember:
The Q&A format of SE is a very specific tool. Quite sharpened toward finding answers/solutions. It may not be great for other purposes, but it very well fits the one it has, and that's the very reason I'm here: Going for distinct knowledge in a solvable and concrete fashion.
There are countless discussion places for RC like topic, from classic style mailing list all the way to modern forum software. They all do support free form talks - RC.SE being none of them