But Twitter, which is based in San Francisco, has been skittish about making major changes to the service, seemingly paralyzed at the thought of scaring off any members of its loyal fan base. In January, when several news outlets reported that Twitter was considering extending the character limit of tweets in a project known as “beyond 140,” users revolted en masse. In March, Mr. Dorsey took to Twitter and the airwaves to assuage fears that the company would greatly alter the way a tweet works. 

Now with the new changes, Mr. Dorsey can have it both ways: keep the 140-character limit while also allowing tweets to be longer.

The compromise is another attempt by Mr. Dorsey to simplify the complex, esoteric rules that have evolved around Twitter and that have made the service somewhat impenetrable to new users. He has made it clear that nothing is off the table as he tries to turn the company around.

With the changes, Twitter will also end another longstanding, frequently confusing convention: Tweets that began with someone else’s user name — say, a tweet from @MikeIsaac (this reporter) to @fmanjoo (the New York Times’s technology columnist) — would be seen only by people who followed both users.

To get around this limitation, users would often put a period before the user name at the beginning of the tweet, a workaround that is now commonplace. But many casual users of the service were not aware of the constraint, or that their tweets were not viewable by their followers because of it, Mr. Dorsey said. Now people will no longer have to add a period to the beginning of a tweet to display the message to all of their followers.

Twitter users will also be able to quote and “retweet” — or rebroadcast — their own older tweets, which was not possible before. The idea, according to Twitter, is to resurface old ideas that may have gone unnoticed.

“Changing the nature of tweets is risky for Twitter, as these qualities have attracted and retained the most loyal users,” said Brian Blau, a technology analyst for Gartner. “But for them to become mass market and move to the next level, they need to make fundamental changes.”

Hmm, somehow Twitter seems less special due to this.