No, I wasn't questioning the use of the "Insert" button, but only wanting to be sure that the right code was appearing in the brackets. Evidently that's not the problem.
I'm using Firefox 57.0 for Ubuntu (Linux) version 17.04.
Thank you for editing out the attachment postscript in "The Post". If I were to enter the code manually rather than using the Insert button, would I just copy and paste the uploaded picture ID, then in the text body manually bracket it with the "attachfull" and "/attachfull" codes?
It seems to me that I did try the method of copying and pasting a picture into a post, and it worked, but still got the postscript.... I think.
I should try posting a picture using my office computer, which has Windows 7 on it, with Firefox or Chrome. Months back I believe that I'd figured out how to do it. Perhaps the problem is the Ubuntu O.S.