The tweet called special attention to Iran's Jews -- there are thought to be perhaps 25,000 living largely in peace -- but it's the reference to "all Jews" that seems especially significant. Given the long-standing enmity between Iran and Israel, and the years of official Iranian rhetoric condemning Israel in often anti-Semitic language, this is quite a shift.
After eight years of fiercely anti-Israeli rhetoric from former president Mahmoud Ahmadinejad and his government, rhetoric that often veered well into anti-Semitism, it's difficult to separate discussion of Jews in Iranian political discourse from discussion of Israel. That's obviously not a particularly helpful habit. But the point is that this tweet, purportedly from Iran's president, seemed to be offering a very small gesture of goodwill at least partially toward Israelis, who can usually expect nothing but hateful rhetoric from Iranian rulers. It's not exactly a unilateral declaration of peace -- tomorrow, Iran will probably still support Hezbollah -- but it's yet another hint of Rouhani's efforts to dramatically soften Iranian foreign policy and rhetoric.
The Twitter account is not officially verified or formally acknowledged by Rouhani, but is generally considered by Iran-watchers to represent his office. Although many Iranian officials have social media accounts associated with them, including Supreme Leader Ali Khamenei (whose Instagram account often posts photos not found elsewhere, seemingly verifying its authenticity), they are never openly acknowledged, likely because the government blocks these same services on Iran's Internet. The only exception came just two weeks ago, when new Foreign Minister Mohammad Javad Zarif publicly acknowledged his Facebook account and then his Twitter account. Rouhani's Twitter account acknowledged Zarif's, a hint of a connection. But maybe most convincing is that Rouhani's official spokesmen have never bothered to disavow the news-making English-language Twitter feed.
The question of Rouhani's rhetoric toward Israel and the West is a remarkably sensitive one, in part because the world is still hunting for clues as to whether this new Iranian leader is really willing and able to do what it takes to achieve peace. A tweet from an unofficial account associated with the president is in itself obviously not a tectonic shift. But it's worth keeping in mind that Rouhani is constrained by his own domestic politics, which include hard-liner factions and which make even these small gestures far from cost-free for him.
In a sign of just how unusual this is, Haleh Esfandiari, head of the Middle East studies program at the Woodrow Wilson International Center for Scholars, told al-Monitor's Laura Rozen, "Not even under the monarchy do we remember such a message."
Update: Fars News journalist Sadegh Ghorbani reports that a Rouhani spokesperson says that the president does not have a Twitter account. The spokesperson did not directly dispute the English-language account or say the tweets don't represent Rouhani's views. The non-denial denial is perhaps in response to the Western media attention to this tweet, but it raised more questions that it answered. Tehran-based reporter Amin Khorami, Al-Monitor's Arash Karami and others say that the account is actually run by the media office of Rouhani's presidential campaign team. The campaign has been over for a couple of months, so it raises the question of whether the people running the account continue tweeting in an official or unofficial capacity and whether or not they coordinate directly with Rouhani or his office. The prevailing speculation among Iran-watchers is that Rouhani may be keeping the account semi-official to inure him from criticism by internal hard-liners while allowing continued gestures of good faith toward the West. Although one Iran analyst suggested to me that Washington may be overstating the account's significance in representing Rouhani's views.