Originally Posted by
SuperKirby
Wow, thanks for the data point. So maybe I should not check-in online JIC.
Since US carriers let you choose seats whenever you want, I would strongly advice you to do just that. The BA agents tried pretty much every trick they could come up with and finally the explanation I was given was something like "since you are already checked in to that flight, we can't do anything check-in related (like adding baggage)".