None of that comment seemed unreasonable to me - I've had large over-ear sets of headphones that require me to turn the volume up pretty high. It takes more to drive them, that's why some people own headphone amps.

Compare that to IEM's like the Sennheiser cx 300 - 5% of max volume at my computer might be too loud.

And it would surprise me if headphone usage at reasonable volumes is worse than going to loud concerts, even if you use headphones for long periods of time. If I'm at a concert or a loud bar for an hour or two, my ears feel really fatigued afterwards, everything seems quieter. I've never turned up headphones loud enough to experience that.