I've recently finished watching up to day 104 which seems to finish up the 2d lighting stuff. At the end of the lighting discussions Casey was able to show reflections from above and below an object. However, throughout the lighting episodes Casey never went into how to solve the problem of reflection through the middle of an object in 2d. I've searched around a bit and couldn't find that topic. I was wondering if Casey ever did figure out how to properly light the middle portion of objects in 2d or if he finished the 2d lighting stuff at all and what episodes those are.
I don't think Casey's gone back to that. At the moment, handmade hero uses a mix of 3d graphics (wall and floor) and 2d sprites for characters, with lighting using raycast to simulate global illumination.
There is no such thing as "properly" lighting in 2d game. Because real light works in 3d. So any 2d game just uses bunch of tricks or approximations to achieve the look they want. It all depends on what kind of look you want to get.
You can search for developer talks about 2d games you liked. Often it the game looks good there are articles or videos about them because people asked about it (so you can also ask a developer for information).