It's not so much about which is better: it's about the fact that we need consistency. At least with "leave it to the browser", there is some consistency and use

It's not so much about which is better: it's about the fact that we need consistency. At least with "leave it to the browser", there is some consistency and users can learn to live with that consistency (e.g. by writing longer posts in a text editor and copy-pasting). When everyone does it ever so slightly differently, you are lulled into a false sense of security. I don't mind software sucking, so long as it sucks in a generally consistent way.