Originally Posted by RealHJ

Hmm, that is odd. I've had it where before DL would just display the MU seatmap but wouldn't allow to select seats. For the last few months, however, it has worked to save the seat and it does seem to actually save it and push it through to MU (same for KE; also before could only see seatmap but not select seats, but last few months it works to select it, and checking on koreanair.com it does save and carry through).

May be it works for some MU flights and not others.. odd, though.

EDIT: I just checked and seat selection on delta.com still works, on both MU and KE. Before it used to work like a year ago for a shortish while, then went to view only but can't select seats for quite a while, but now the last few months it works to select and save the seats again. Hopefully it'll stick around now.