OK Thanks for that. I was right clicking on my name in a post and doing "Profile" you have to go top of page -> settings -> account. Oddly once in the account there is a "back to profile" button but from there I can't see how to get back to settings, other than the top of the page.....
Had not tried editing a sig, but I had noticed right after the migration that the "show signature" option in my profile was turned off, even though it had been on previously. Of course I turned it back on, and then I at least saw some posts with sigs.
I'm curious, what else was borked there?
If the the change did not alter user's profiles, many people may still have viewing sigs disabled.