For MySQL 4.0 compatibility, store a summary of actions in the abuse_filter table.
While I'm there, make the pseudo-internal names for actions localisable and therefore actually make sense to the average user.
* Introduce a syntax check on-save.
* Introduce filter history (requires DB schema change).
* Deprecate now non-working /tools interface (will come back).
* Disallow more than 100 condition-checks per action.
* Disallow filters which are misbehaving (more than 5 matches, constituting more than 5% of recent actions)
* Display statistics for all filters (percentage of times the condition limit is reached, and percentage of times some filter is matched), and individual filters (percentage of times it's matched).