By Thomas Escritt BERLIN (Reuters) -With Twitter in disarray since the world’s richest person took control of it last week, Mastodon, a decentralised, open alternative from privacy-obsessed Germany, has seen a flood of new users. “The bird is free,” tweeted Tesla mogul Elon Musk when he completed his $44 billion acquisition of Twitter. But many free-speech advocates reacted with dismay to the prospect of the world’s “town square” being controlled by one person and started looking for other options. For the most part, Mastodon – named after an extinct breed of mammoth – looks like Twitter, with…