My final internal South African leg was Cape Town to Johannesburg. Mobile boarding pass and online check-in were working fine, straight through security and to the great SLOW lounge.

At the gate (one of the C bus gates), there was a carry on luggage gauge clearly visible in front of the check in desk. When boarding was called, there was no Priority Boarding, I assume as it was a bus gate; and with the first circa ten people, no-one's carry on was checked in the gauge. Onboard, there was someone in club with a clearly oversized bag, but the cabin crew stored it in one of their jacket lockers.

So no problems with my carry on (7Kg ish) luggage on my weeks trip around South Africa.

Interestingly I got a red beep at the gate, to say "1A Emergency Exit Ineligible". The gate lady looked at the computer, shrugged and let me on anyway. I sat in 1A and the seat next to me was unoccupied. I'm not sure what the red beep was about as I've never had an issue with emergency exit rows before?

Hopefully that provides some reassurances about Comair carry on luggage. It seems Mobile Boarding is the way to go, along with not obviously oversized luggage.