* Little sign of Hong Kong protests flagging * Nervousness around National Day flag-raising * Atmosphere on streets resolute, but calm * Torrential rain makes life uncomfortable for thousands (Updates after National Day flag-raising, paragraphs 1, 9-12) By Donny Kwok and Irene Jay Liu HONG KONG, Oct 1 (Reuters) - Thousands of pro-democracy protesters thronged the streets of Hong Kong early on Wednesday, ratcheting up pressure on the pro-Beijing government that has called the action illegal, with both sides marking uneasy National Day celebrations.