I've found that u can use the "quick reply".. in fact, that's all I've ever used when posting a reply cause I didn't know how to use those other buttons.
If you use the "quick reply" you must paste the IMG code that is created on the photo-hosting website..like photobucket.com or a site like that.
And before you hit "add reply" select "preview post" first. If the pic doesnt show up there. It wont show up when you actually post your reply.