Reportedly, the CoTweets feature, which enables the primary tweet author to ask for a second person to be tagged in the tweet and debate its subjects through Direct Message, has been tested by several Twitter users today.

The co-authored tweet needs the second account's permission; while it was written by two persons, comments only appear to be aimed at the original author in the final form of the tweet, reports Mashable.

If one accepts a CoTweet invitation but then decides to not want to co-author that CoTweet, Twitter will say that they can remove a CoTweet after it's published. The first tweeter then retweets the CoTweet as usual.

Also, since only two authors can appear in the header of a CoTweet at a time, users can really only invite one co-author per CoTweet. As a small test, some accounts in Canada, Korea, and the US can now invite others with a different account to CoTweet.

As per Mashable, it is clear that Twitter wants to monitor how CoTweets are utilized before making improvements and formally offering the service to all users given that the company says it is only testing the functionality for a brief period. Twitter states that when this trial is finished, the feature could be disabled and any CoTweets might be removed.