Why does this regularity still match the second space?

To avvoid lines that start with three spaces, look for

^[^\h][^\h][^\h]

@dublove

What exactly are you trying to achieve? 

Remove those spaces? All of them or some? 

Replace them with something else? 

Remove whole line? 

It works fine for me

Don't know why it's so complicated - you could search for a single space (inserted by space bar) and it finds the same thing.

Can you elaborate or provide a larger sample set?