Problem: In some cases of harassment, for example when a long terme abuser discloses personal information about legitimate editors (doxing), there is a need of using private information in an abuse filter (to prevent those information to be disclosed on wiki). As all AbuseFilter editors can currently access it, this is not possible for privacy reasons.
Proposed solution: Create CheckUser-level and Oversight-level abuse filters, only accessible to checkusers and oversighters. Corresponding logs should also be private, obviously.
Who would benefit: AbuseFilter editors, harassed editors, everyone
More comments: Maybe only one type of private abuse filters, accessible to both checkusers and oversighters, would be enough; it remains to be discussed. On the other hand, there may be specific variables handy for checkusers only (see phab ticket below).