After testing it on channel discussion tabs for a few weeks, it's now starting to roll it out to all videos on the site.
The system, which is launching on channel discussion tabs this week before rolling out to all videos over the next few weeks and months, will automatically rank comments and feature threaded and private conversations.
Although the United States and North Korea continued back-channel discussions during the intervening five-week period, they apparently did not bridge many differences.
In an intense series of back-channel discussions with Mr. Lee, senior administration officials, including President Obama, have praised South Korea for its calm response.
Indeed, Mr. Son has held back-channel discussions with Yahoo, as its chief executive, Carol A. Bartz, plans the company's future, people involved in the talks said.
"There were almost certain to have been back-channel discussions between the secretary of defense and Air Force that indicated they were not comfortable doing business with Phil Condit in the future," Mr. Thompson said.
Russia proposed more than three years ago that Syria's president, Bashar al-Assad, could step down as part of a peace deal, according to a senior negotiator involved in back-channel discussions at the time.
For weeks, reports have swirled around the capital of back-channel discussions between the Afghan government and the leadership council known as the Quetta Shura, so called for its supposed base in Quetta, Pakistan.
As he headed to Gaza with an Arab League delegation on Tuesday, Turkey's foreign minister, Ahmet Davutoglu, suggested to reporters that back-channel discussions had been opened with Israeli authorities.
