If they are posting pictures using TinyPic, the images won't show, since we have banned TinyPic images from being shown on the website. This doesn't have anything to do with your browser or your computer. If the tutorials are using images uploaded from TinyPic, this is why you cannot see them. As Arctic said, the comments are probably from some time ago, before TinyPic images were banned, so they had no issue viewing the image content.
Your imgur image may not be loading if you are copying the wrong URL code. I would try uploading an image, select the arrow down symbol once it's uploaded, select "Get share links," and copy the BBCode option. c: