If downgraded from D1 to domestic first (with recliner seats), would ideally want compensation or appropriate rescheduling. Standard on other airlines is that equipment is not guaranteed, just transportation from A->B in the class of service booked, so I'd be out of luck here (now understand this wouldn't be the case). Normally wouldn't be so ornery - but was trying to decide between DL vs B6 for a redeye and wanted to cover my basis in deciding on the former.

The very helpful answers from Emma and all the previous posters have really thoroughly addressed all my questions though! Very grateful for the experts here patiently walking me through everything. I'll hopefully be more experienced and knowledgeable for the next go-around.