Are you sure it's not using sub-pixel positioning
sprite is positioned at 0,0 with origin at 0,0 it has the same size in game as the jpeg being loaded.
with linear sampling enabled? Try setting pixel rounding on and point sampling in project properties, does it still happen?
pixel rounding is on, when changed to point sampling it looks even worse. sharper, but messed up. BUT when I turn off webgl it looks great, just like original, so I believe it has something to do with webgl rendering in browser :(
i'll try and create a capx to demonstrate this...