I tried this and it only loaded one of the 3 pictures and gave me a red box for the other too. It also appears if you do it this way you do not get a space between the pictures which I like to have for easier viewing. But it seems like a fast way to do it.
How I post pictures is I log into my photobucket account. I select the album I want to post the pictures from (cause I have a few different albums).
Under the picture there are 4 different link codes and I select the bottom one which is the IMG Code. I highlight it then right click and copy.
I then paste that right into my reply. If I post more I do it for each picture I post and I put a space between each IMG Code that I paste in my reply box.
I never have luck uploading pictures from my computer with the "Manage Attachments" button here because my picture files are always too big for the required file size so they won't upload. So I use photobucket instead and post them the way I just described.