I tried calling. Turns out that was bad advice. It only made things worse.

Got res agent. She updated my current reservation to include my full middle name, and now my reservation does indeed show my full middle name.

But in the process the other person on my PNR ended up on a separate record (actually, she kept the original confirmation code, and I got a new record.) So she is now no longer on the upgrade list for the return. (We both already cleared and have F seats the whole way on the outbound.)

Res agent then transferred me to mileage plus to update my profile there. They swear up and down that everywhere it says MIDDLENAME, not MI. And this should be accurate - I just got my latest United Club card, for example, and while my card from last year says FIRSTNAME MI LASTNAME, my new card does indeed say FIRSTNAME MIDDLENAME LAST NAME.

So I go and book my next ticket. Through the entire booking process, my name only appears as FIRSTNAME MIDDLENAME LASTNAME.

But I just got my ticket in email, and I'm back to LASTNAME/FIRSTNAME(mi)MR as the name on the ticket.

So, messed up my ticket, and didn't fix my profile.

This is extremely frustrating.