Adding a data point:

I had two tickets, one from DTW-MDW, and another from MDW-HND, all on Delta stock.

Agent first said it was not possible to check through because this was ‘skiplagging’. I pushed back and said I’m not skipping any segments.

Red coat came over to clarify that indeed checking bags through 2 tickets was possible. It took the agent another 15 minutes but tags eventually got printed (though the agent couldnt print bps for the second ticket)

Carryon barely fit the overhead on the E175. GA wanted to gate check it but acquiesced when I said I was connecting at MDW (which is probably unusual). GA could only print tags to MDW