? I would love the option to ban from my linked journals by IP address rather than username.

We will almost certainly never allow any form of banning/blocking/filtering by IP address. An IP address is not a unique identifier: one person can use multiple IP addresses, and one IP address can be used by multiple people. There's a real tendency for people to treat IP addresses as absolute identifiers, and (worse than that) the absence of an IP match as definitive proof that two accounts aren't owned by the same person, and none of that is true. For instance, when I don't care, sarah and I would look like the same person to anyone using IP information, and if I did care (which I really so don't) it would be literally three seconds of work for me to post with any one of thousands of IP addresses. So, it's really a false sense of security, and people shouldn't be relying on IP addresses for absolutely anything that has to do with identification.