Message Editor Interface settings?

[Howard]

OK after a bit of mucking around, I have found this.
If I "post reply" to this thread we are actually looking at now, my interface looks like this:
editor 3.jpg
So images are attached using the (paperclip) "Attachments" button.
However, on SOME threads when I hit the "Post Reply" I get a slightly different interface, thus:
editor 2.jpg
This one has an additional button, the "Insert Image" button where I can link to an image on another web site such as Photobucket or even Shedfull. But this button does not appear when I reply to some threads, this one we are reading now, for example.
editor 4.jpg

[Howard]

Now, I have managed to create a post with both the styles of attachments. I assure you, this was not planned!
Interestingly, all 4 attachments were uploaded using the same method. However, the one shown in the "Attachments" box at the base of the post was the only one not posted in the composition of my post. ( Gawd, this is sounding complicated, doesn't it?! I am sure it isn't as complicated as I am making it sound...)

[Howard]

So testing once more...

This post was created by uploading the three photos, but not actually attaching them to the post... ????
Also, my editor interface is set to "Standard Editor" and IIRC I have never changed this setting.