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ESports tournaments, such as Dota 2's The International (TI), attract millions of spectators to watch broadcasts on online streaming platforms, communicate, and share their experience and emotions. Unlike traditional streams, tournament broadcasts lack a streamer figure to which spectators can appeal directly. Using topic modelling and cross-correlation analysis of more than 3 million messages from 86 games of T17, we uncover main topical and temporal patterns of communication. First, we disentangle contextual meanings of emotes and memes, which play a salient role in communication, and show a meta-topics semantic map of streaming slang. Second, our analysis shows a prevalence of the event-driven game communication during tournament broadcasts and particular topics associated with the event peaks. Third, we show that 'copypasta' cascades and other related practices, while occupying a significant share of messages, are strongly associated with periods of lower in-game activity.