Plus: for some f*cking reason, i can't post images directly, because of this goddamn message: You are not allowed to use that image extension on this community..
When you upload to Imgur you have to right click on it and get the share links. Look for the BB Code, this is the one that can be used here.
Basically the reason you can't post directly is because your link doesn't have the image extension on it. Pngs are the best. I don't know any other extension that could be used.