I think the discussion is on aerodynamic lift rather than thermal lift.
Precisely. That's what keeps both aeroplanes and gliders in the air. Jongster was considering the thrust vector when climbing under engine power and the thrust is greater than the drag and is perfectly correct. In a glide (and aeroplanes can also glide even if not quite as well) one Is always flying 'downhill' with no engine thrust and only climbs due to the air it is in rising faster than it is sinking so it's a combination of aerodynamic lift and drag. Perhaps Jongster's point is also valid for a glide and weight and lift are equal only in true level flight.