Computer Help and Support

It looks like it's a very unintelligent clipping - in the text I gave in the OP, the 2 images were wide, but short from top to bottom, but were made unnecessarily large from top to bottom, and clipped beyond usefulness from side to side. So the clipping algorithm seems to be "2 images - put them side by side, and enlarge them to take up the whole room top to bottom, no matter how much clipping that needs left and right". If they just had something saying "these would fit better one above the other", it'd work a lot better.

Also annoying for this (I'm just venting my frustration at Twitter, which I think is a really lazily designed interface) is that when viewing the tweet on Twitter, the pointer doesn't change when hovering over the image, so there's no indication that a click will get you a different view; and when you do click, they superimpose the text of the tweet on the full-size image, and you have to move the pointer around to get it to go away.