I'm thinking of (maybe) manspreading
What made you come to this decision?
I just don't want to share my space. No special reason
Not everyone is going to be as willing to share their space. You should check if it is okay before you go around invading spaces.
Pfft. Who cares what they think if I do it?
They care and they might complain that you are invading their space. It would be good to respect their space and not spread your legs.