This is worthy of a whole book, but I'll try to touch on a few points.
Galvanic corrosion is a DC problem of dissimilar metals in contact with one another, either directly or through an electrolyte. The galvanic isolator on your boat will block DC currents, up to only about one volt, so that your neighbor's boat and yours cannot complete a galvanic DC circuit through the shore power connections.
But the galvanic isolator will allow AC fault current to pass, so that if your grounded microwave shorts out, it can carry enough current back to the panel to trip a breaker. The shore power ground must be bonded to DC negative. Mine was done from the AC panel ground bus to the cigarette lighter negative on that panel. If you don't have, or remove this jumper, it's likely you'd have less corrosion issues, but you can't do it for safety's sake.
The bonding, (not grounding) system on a boat is there for life safety.
Say, you're working with a drop-light, drill, whatever, and the frayed cord touches some metal thing on the boat. What you want to happen is that the high fault current flows through the thing, through the bonding jumper, to the AC panel ground, and trips the breaker.
If the thing wasn't bonded, then you could receive a shock if you got between it and another surface that was grounded (AC appliance), or bonded (motor, etc.). This isn't likely on a C-Dory, but is a real issue in the bilge of a big boat.
None of this has anything to do with stray current corrosion. Let's say your boat has a bilge pump whose splice is sitting in a puddle in the bilge. It isn't a dead short, so it doesn't blow the fuse, but it is creating a 12 volt circuit to a bonded piece of equipment, your through-hull. The galvanic isolator isn't going to help, because the circuit is contained on your boat, and if it were from your neighbor's boat it still wouldn't work because it can't block more than about one volt. Stray current corrosion can happen very quickly, hours or days, while galvanic corrosion takes time.
I know this is confusing, I read and re-read that excellent article in Passagemaker a few times, and it's still sinking in. And I'm even an electrician. If I've misinterpreted any of this, I hope I'll be corrected.
IMHO, don't bother bonding the through hull.
