the legitimateness of your bank statement. Some lenders would probably be fine with the account number marked out. But if the underwriter is requiring it then arguing with them over it is a losing battle and not one worth doing in my opinion.

I also wouldn't be too worried about them getting your account statement. As a loan officer I look at like 10 new account statements every day. I haven't met a loan officer yet that would risk their job (and any chance of working in the industry again ever) for access to an account number.