Steve, I'm sure all the steps you outline are helpful but the fact that for a while I was locked into "digital signature" mode and then somewhat arbitrarily I was reverted back to "electronic signature" mode implies some sort of bug since I did none of the things you suggest.
For the original poster, all I can offer are the steps I took after I saw the same thing you saw:
. my Adobe Acrobat XI updated and out of nowhere when I "Placed Signature" it asked to draw a box and create a digital signature whereas before it overlayed a transparent e-sig.
. I went into preferences/signatures and in one of the 4 settings buttons where it shows your digital IDs I deleted all that I could.
. I created a new digital ID and instead of clicking the option to save locally I said use Windows
. I the "Placed Signature" and again was required to create a box and digital signature but I did it anyway in a PDF.
. I then "Placed Signature" a SECOND time in the same PDF and then out of nowhere it no longer asked me to create a box but I saw the transparent e-signature I used to see in older releases of Acrobat 11.
. From this point forward I got the eSignature as desired.
Good luck.