Also, if it is a Gyazo image, when you are on the actual capture/image page, you can click the Share symbol at the top and then click 'Copy direct link'. Then you don't need to add the ".png" part - it is already part of the copied "direct link":
And if you are in a New Post or Reply window (as opposed to the Quick Reply window), then you can click on the Image icon and paste your link into the little box that pops up and it will automatically surround it with the 'img' tags:
So the actual contents of the above stuff looks like this, before actually clicking the Post button. i.e. the image links are not yet resolved to pictures - that happens when you finally click Post: