LONDON, Aug 24 (Reuters) - More than a dozen of the world's biggest tech companies face unprecedented legal scrutiny, as the European Union's sweeping Digital Services Act (DSA) imposes new rules on content moderation, user privacy and transparency this month. Across the EU, a host of internet giants – including Meta's (META.O) Facebook and Instagram platforms, Chinese-owned video app TikTok and a handful of Google (GOOGL.O) services – are adapting to the new obligations, including preventing harmful content from spreading, banning or limiting certain user-targeting practices, and sharing some internal data with regulators and associated researchers. The EU is seen...