comment box adjustments twenty ten/weaver

I am using weaver under twenty ten theme and I would like to know how to change the size of the comment box, please. Also I would like to hide or erase the html code under the comment box. I searched within the forums and I saw different answers and some of them said that the html code cannot be erased.

In case that there is another plugin for comments I could use please give me an advice about it. I need to have an email address field to be filled in if possible.

Thank you very much for help.