Some harassment comes from anons, as was this case with https://en.wikipedia.org/wiki/Special:AbuseFilter/792
It'd be great to allow not only entering in IPs, but also IP ranges. Right now for the above example, if I want to see if there are interactions, I have to enable the filter and wait to see the results (or painfully cross-reference using Special:Contribs). This means we have to employ the expense of a filter solely for observation purposes. If I could check for interactions ahead of time, I'd be able to play around to find out which IP ranges need to be targeted, or discover a filter won't be useful at all.
Introducing this feature might be a bit challenging on the frontend, but the backend shouldn't be so bad. For single IPs, you can use `rev_user_text` (which you're probably using now).
For IP ranges, you can take advantage of the `ip_changes` table, and target a range with something like `ipc_hex BETWEEN 1234 NAD abcd`. If/when you get around to this, I'm happy to help :)