Kylotan
If a feature says "Non-destructive MIDI editing" that should in no way imply "cannot delete holes".

I dunno...if you try to delete a section that contains MIDI data, and you had chosen not to destroy MIDI data, then the MIDI data would remain intact despite asking data within the hole to be removed. IOW I guess saying "don't destroy MIDI data" trumps an action that could destroy MIDI data.
 
I agree it would certainly make more sense when deleting holes if MIDI audio was treated the same way as audio data, but presumably, non-destructive MIDI editing is intended for some other reason and it just happens to affect the hole thing as a by-product of its existence. Maybe the solution would be for SONAR to recognize that whenever delete hole is chosen, NDME is suspended for the duration of that operation.

I see what you're saying, that it shouldn't delete MIDI data if I've asked for non-destructive MIDI editing, but it's not like it'll prevent me from deleting a MIDI clip any other time, even with that setting on. If I choose to delete an area that contains MIDI then I just have to accept the consequences. Ideally the algorithm should slip-edit any clips that extend beyond the area to be deleted (thus preserving their data for later) but completely remove clips that fall entirely within the zone. It could even pop up a warning box about this, listing any clips that will be deleted that don't appear elsewhere in the project.