A Study in Bending and Breaking the Rules
In analyzing real texts, you will find that sometimes writers join main clauses with a coordinating conjunction ("and," "or," "but") without a preceding comma, or they join them with a comma without a conjunction.
1. Then every one sat down and dinner
2. They live wicked lives, therefore
they ought to be punished.
3. They became very, very great friends and Little John was next to
Robin in command of the men.
4. This isn't money I have in my
bags, it is only pebble stones.
5. She loved me too and we were
6. These fifty years have I come and gone to Nottingham market,
and I have never seen the like of it — never. He is ruining the trade,
that's what he is doing.
7. I love the sound of the harp and you can play some sweet music