EDIT: Reposting because I think it's useful, and there are always problems with images being too small etc.
This browser extension is for you. The page has downloads for Opera, Firefox, Chrome and Safari.
What it does: when you hover over thumbnails, it expands them to full size or to fit your browser window, if it's too large. It does so on basically every website using images, not only here. As you can see, it works on most of kinja'd images with no expand button. It also works on some pictures with the button. Also in comments, in most cases. I use qualifiers because Kinja seems to not like the extension and it can be wonky.
Note 1: installation on Chrome is a bit convoluted - you need to download the extension file, then drag & drop it on the Extensions page in Chrome.
Note 2: If you want to have the expanded images centered like in the examples, you need to go to the extension's settings > Hover zoom tab > Pop-up placement and set it to "center".
Feel free to share this to other Kinja sites.