Re: User email address encroaching on post content
So they’re using their email address as their username? That seems like a bad idea from a spam perspective (i.e. posting it means they might get more spam.)
Making things wider is going to be done in the style.css file. You would find the div that you want to make wider, then just increase the width. You would have to make the wrapper div wider to enable everything inside it to be wider. Once that wrapper is wider, just make the divs inside wider, or put more padding or margin in there to space things apart.
It’s all in the style.css of your theme though.