CI 400 is somewhere in the region M0.85 to M0.86, the same as a B747 or A380 cruises at.
Has been .853 most flights near optimum.
It won't break the jet or kill your pax.
It might be smoother at M0.82 if you're in some turb, guess that's up to you.
Apart from tending to reduce descent speed from 325kt (bit close to the pole when in VNAV PTH for this chicken) I don't have a problem with it. If they get another flight per year out of me, who cares? Still same workload for me. Otherwise, I get home 10 mins earlier every sector!
Seems stupid though, those 10 mins (or 20 for two pilots) are costing about 2000 kg of fuel, or around $100 per minute.
Expensive pilots, I'd almost do >92 hours for $6000 an hour!!