evidence: Elon Musk's Twitter is threatening to take Facebook's parent company, Meta, to court over its new rival social media app, Threads. The night that Meta launched its new text-based app, Alex Spiro, Musk's personal lawyer who also helped with his takeover of Twitter, sent Mark Zuckerberg a formal letter regarding Twitter's "serious concerns" about the legality of Threads, as Semafor first reported. [...] Public tension between Musk and Zuckerberg has been heating up in recent weeks. The two men even passive aggressively challenged one another to a cage match, something very unlikely to happen, according to Musk's biographer, Walter Isaacson. Since launching Threads on Wednesday, Zuckerberg has taken several shots at Twitter and Musk, eagerly posting about the now over 30 million sign-ups Threads has seen.