(Reuters) - Comcast Corp on Thursday reported its best quarter of broadband net additions in 12 years, but revenue fell shy of Wall Street's estimate as the coronavirus pandemic hurt advertising.In the first quarter, Comcast gained 477,000 broadband subscribers, beating analysts’ average estimate of 364,000 net additions, according to research firm FactSet. Revenue from the business grew 9.3% to $5 billion(4.00 billion pounds).Comcast experienced a spike in broadband use and a shift in usage..