As it happens, I could get the armrest down on a standard coach seat. There was definitely hip compression going on, it wouldn’t be comfortable long-term…but it was down.
The man of the house has broad shoulders. I mean, I have broad shoulders, and his are broader, and the two of us sitting together in 2 standard coach seats? Did Not Fit. To our minds, the (empty) second seat was worth it.
I also had an interesting conversation with two of the flight attendants on Saturday when I asked if there were unbooked seats on the flight. One was quite versed in Alaska’s “second seat” policy and recommended I check with customer service as soon as possible about my refund. The other, a gray-haired gentleman who’d been joking throughout the flight, seemed appalled. He pointed out that there’s no universal way to know who will fit in the seats before boarding, and that even if the armrest does go down, things like shoulder width can be just as troublesome. The other flight attendant was nodding in agreement, which felt nice.
He also said that he hoped that no one had made me feel bad or uncomfortable about my size while booking my tickets. I told him no, quite truthfully, and that getting a second seat on my own let me feel in control. He also offered a complimentary cocktail, which I would’ve taken him up on if I hadn’t had ibuprofen. :)