[#479] Update text to encourage user to log back in again w/codename

*Some* work for #479, based on a conversation I had this wk w/@dolanjs & @garrettr. Basically giving submitter as much guidance as possible on what they should expect, what we expect, what they should do next.

Wouldn’t mind some editing to make less wordy, but I think I hit all the places where some explanation/guidance could be used. Also as conversation in #479 notes, we could also describe where to keep the codename, etc. etc
`.format` is slightly preferable to `%` for string formatting, but we use them inconsistently so this is fine.