I always drive in B mode as well. I hope I'm not hurting anything. The salesmen said it wouldn't hurt anything but I don't think they know anything about the cars.
It shouldn't hurt anything. But do understand that it's less efficient than driving in D mode and coasting whenever you can. I mostly drive on the same city route every day, so have learned when the let my foot off the gas and begin coasting, and the car will have slowed enough by the time I hit the next red light that I need minimal braking.
Electric regenerative braking is only about 30%-35% efficient. That is, after you add in the losses converting kinetic energy to electric, losses charging the battery with that electricity (batteries don't store electricity - they convert it into chemical potential energy), losses extracting that electricity from the battery, and losses powering the electric motor, only 30%-35% of the vehicle's original kinetic energy can be converted back into kinetic energy later. Race cars with regenerative braking systems (KERS) use a flywheel instead because those can be up to 70% efficient.
I've talked with some Tesla owners while charging, and they were actually jealous that you can coast like this on the e-Golf. Apparently Tesla imposes a 5% regen rate in their "no regenerative braking" mode. So they cannot coast as well as the e-Golf.
Also, from watching dashcam video channels, I've found that other drivers can be confused if you drive in B mode. Whenever you let off the accelerator, the car immediately starts slowing and the brake lights come on. Other drivers can interpret this as you brake checking them, and get upset at you. In particular when someone honks, the natural tendency is to stop accelerating and look around to figure out what they're honking about. In D mode, all that happens is you stop accelerating. But in B mode you immediately begin slowing down. If it was the person behind you who honked, this can look to them like you hit the brakes in retaliation for them "honking at you".
(You should also avoid B mode when the battery is nearly fully charged. But the car already handles that for you. If you switch to B mode while moving with a near fully charged battery, it won't slow you down as much.)
