will have to wait for Andy in the morning… not sure where he was going here…

I can only take a guess that your WordPress theme styling is playing a part here. We are making some minor changes to the display of the pre-supplied WordPress smileys which will be in the next update (5.5.6). These might help. But if this is the WP theme then it might be hard to track down although it might be worth you looking at how the theme styling handles images on smaller devices – probably within @media clocks.