Just booked our first comfort seat (not a COS, just wanted the whole row.) Booked over the phone a couple of weeks after the original booking; cash was unreasonable, but miles was not bad; agent proactively saw we had B and C seats, and moved one of us to A and put Exst in the middle. After getting a human, it took about 12 minutes on the phone, much of it on hold for her to process the request. New PNR for the Exst supplied on the phone; email came through a couple of ours later.

Questions:

• Do we check in Exst? (Other threads suggest yes, but only at airport?)
• Do we scan Exst’s boarding pass at the gate? (Common sense suggests yes, but checking. Also, how does the ops agent respond when two humans present three boarding passes?)
• (Known: Exst can earn base miles; must call later to get them.)
• (Known: Exst does not get their own carry-on.)
• (Known: Exst by choice (not COS) is not eligible for post-flight refund request.)
• Any other tips, gotchas, etc?

Thanks.