bi-wire cables on single binding post, sonic loss?

If you connect the wires together at both ends (amp and speaker binding post) then technically this is so little different from a thicker gauge of wire as to be of dubious benefit = think about it => you are shorted at both ends so the signal must be the same at both ends the only difference is a lower path of resistance between the two points as you have presumably more wire thickness between the two shorted points.

Bi-wiring works when the speaker allows separation between woofer and tweeter - this means a crossover that is designed to allow bi-wiring. In this case you can use a separate amp to drive each cable and reduce IMD distortion from driving 20 to 20Khz with one beleaguered amp (especially the high current demands of a woofer). Remember that an amps life is much easier if you restrict its load and the frequency range that it needs to cover.

Bi-wring also works well with bi-amping as in a setup using active crossovers => this will probably give the most benefit as the amp does not have to deal with driving a passive crossover so life gets even easier for the amp.

I was just wary of negative effects that anyone might have experienced to be a show-stopper.

Absolutely no negative effects. You can wire this up and it will work great provided you don't mix +/- or red/black on the four spades at the speaker end (which could short out your amp if you are not careful).

I quite agree - I never liked the Bananas.