I set off with my 5 week old DS yesterday on our first solo trip. We got on a pretty empty train, I folded the buggy thing and wedged DS nicely on the seat next to mine. He went to sleep. Near London, loads of worker bees got on (though we were out of commuter hours) and pretty much filled up the train. Some were left standing. A man next to us looked rather pointedly at DS slumbering on his seat and I felt I should pick him up and have him on my lap so he could sit down. But I didn't. In my defence, there were two other seats in the carriage with bags on that he could have asked to sit in. And DS was dangerously near feeding time and if I'd woken him up I would have had to breastfeed him surrounded by men (I've only bfed in public a couple of times before and both times have been a bit hectic with DS 'forgetting' how to do it, revealing my nipple to waiters, etc.).
I thought of standing myself, but I must admit, I didn't do that either.