I think you understand the Forum software function correctly.
In my experience, a single attached image file will appear at the bottom of the post, but only if there is only one attachment. I know that works for .JPG and *.PNG files.
Because that is sufficient for most of my purposes, I haven't (despite being a forum member for a very long time) spent time learning and using the Insert Image feature for links to hosted-elsewhere or hosted-by-PLCTalk images.
I tend to prefer not to tell a story in multiple images, but sometimes it's necessary. I try to trim mine down in size; Paint.net is my go-to utility.
This forum's software is relatively antiquated, but it's free and stable and seems to suit its community well.