This seem unnecessarily confusing. Your info in the link refers to "advanced" reply vs quick reply while your website icons say "post reply" vs "quick reply". IMO, there should be one reply window that shows up after someone clicks "reply to this post" or "replay to this thread". In either case, pictures should be allowed.
Its also confusing that the icon above that says "insert image" is not how pictures are inserted. Instead, we need to go to the "advanced reply" and "attach". Most of us think "attach" means it shows up as an attachment vs a viewable image.