Jagex would lose money if people played longer. They make money on a monthly basis, not hourly. If people play longer then at any given time more people are playing and more servers are needed. It could be argued that Jagex would lose money, but I don't think people stop because of yellow text (and if they do, they've been playing too long anyway). If it strains your eyes, turn chat off, but otherwise yellow is good because it stands out over most terrain and objects without being overly bright. Turning chat off is KEY