I have to agree with Ryan. While there are potential privacy issues by
identifying users via IP, it would play merry hob with folks who would log
in under their main account to make a point, and then log out and support
that argument as an "Uninvolved" IP Address. There were several problematic
blocked/banned users, where the only way for non-checkusers to identify
these problem users is via IP Addresses. To require Checkuser to verify
EVERY such account instead of the general public would noticeably increase a
Checkusers workload.