Fourth quality: ability to count

there are four kinds of people: people who can count, people who can't, and pedants

I think "caring" is probably the only one that separates the best from the rest. Reminds me of this: https://youtu.be/7EmboKQH8lM?t=2165

If we care as a developer, we write better code, learn things and listen to our team, customers.

Also the ability to identify off-by-one errors

I love this comment, not least because the enumeration leaves one to imagine what level of multi-dimensional punning and irony are being invoked.

To be completely honest, it was a mistake... I forgot to add 'curiosity' after 'caring' but... I will now use this to figure out who is curious about the fourth one :D

And debugging off-by-one errors.

That's only 3

There are only two types of people: those who can derive a set from missing data.