What do you look for in damping factor?

Audiokinesis, high damping factors don't automatically indicate high global feedback.
So high damping factor does not necessarily imply sonic trade offs in other areas.
As you've posted in earlier threads, it's easier to make a speaker with a low impedance to have an ultra smooth impedance curve, so there are no impedance curve bumps to modulate the frequency response. Typically speakers with such a low impedance are driven with amplifiers with high damping factors.
Are you suggesting that your bumping the impedance in the bass region to correct for a fundamental flaw? Using a port will of course compromise phase and time accuracy.
Th impedance curve of the Maggie's will work well with high damping factor amps well.
I would suggest choosing a speaker that fits into ones budget, room accommodations, listening tastes, then choose the appropriate type(s) of amplification, and then make ones final amplifier choice.

Atmasphere, thanks. That appears clever, but I still think the use of ports come with a price. So much for free lunch?

Of course those are all good reasons to like a speaker, but, amongst other things, ports can compromise time and phase fidelity. Obviously, some feel the trade off worth it.