The new Comfort Diner at 399 Grand St. is in soft-open mode this week. Local residents have taken note of signs posted outside listing “preview hours” from 5-9 p.m. and a 20% discount “off the entire check.” Last night, owner Ira Freehof told us he wants to make sure all of the kinks are worked out in the kitchen before launching full-scale service. Right now, the restaurant is hosting a limited number of guests per hour. By next week, Freehof said, he’ll launch breakfast service, with a grand opening expected in two weeks. Next Tuesday, the State Liquor Authority will weigh in on the Comfort Diner’s liquor license. In September, Community Board 3 voted against the liquor permit after Freehof declined to accept restricted hours. An original branch of the restaurant has operated in Midtown for 18 years.