From what the user said so far, it doesn't sound like they did ANYTHING wrong.
If you base your decision on the experience of one user with a problem (who doesn't even share the story first-hand) instead of the millions of users who don't have problems, then indeed you shouldn't buy a Trezor.
By the same logic you should probably not use Windows. Or any software for that matter, because there's always someone who's had a problem with it somewhere.
i'm not sure I agree with our logic there but I get the general gist of it.

the main question that comes to my mind is before the firmware reset why was the thing "greyed out" and unable to be used?? that doesn't make any sense. maybe trezor would know since they are the ones that designed it. if i was the OP I would have contacted them right there and then and demanded to know why before doing anything else. but unfortunately they reset the firmware and when they did that it really messed things up. probably forever.
another mistake they made is losing their PIN and thus causing them to feel the need to reset the device. that was a big mistake.