To answer your question, since the other replies are being disingenuous, it's a dog whistle for groups including 'liberals', left wingers, and - historically - Jewish people. This is why the OP comment makes the unsubstantiated claim that it's a method of coordinating an in-group's thought - as though agreeing with a left-wing bias Twitter is because of brainwashing and propaganda.

It's unsubstantiated because it's easily proven wrong. Twitter was home to Trump's presidential campaign. It's home to groups like ISIS, the Western output of the Kremlin, of the CCP, of Bolsonaro. Of Musk.

There is a point to be made about the changing role of Twitter. In my mind it is for some definition of 'elites' - but for expressing their views to their followers, not for coordinating. Sad that this opportunity to discuss such has been co-opted by conspiratorial rhetoric.