So you want to link an image in a comment? Like, maybe, this one:
This is from the following website
So how do you do this?
Key points to note
1) ALWAYS ALWAYS ALWAYS put a title. This is for the convenience of those who may wish to minimise the comment
2) The format is !imageurl! (or you can just click the little tree icon and enter the URL)
3) The preview button is there is you wish to check your work
4) ALWAYS PUT A TITLE (yes this is here twice for a reason)