inline images in twitter feeds

I'm not sure if Twitter changed something recently, or if it's just taken me this long to figure this out. For the longest time, I couldn't find a way to have images that people post in their tweets be displayed in-line. Instead, a link would be shown for each image, and I'd have to click the link to see the image. I supposed that it was because I don't (yet) have a Twitter account, and that perhaps to encourage people to sign up and log in, Twitter doesn't want non-logged in people to be able to see images in-line.

But now I noticed that when I click a link to a twitter.com/*** page with JavaScript disabled, it redirects to mobile.twitter.com/***. On the mobile page, even if I enable JavaScript, the images still only display as links. But if I re-load the non-mobile page with JavaScript enabled, then it doesn't redirect, and the images display ok.