So:

elseif ( $wgDBname == 'metawiki' ) {
$wgAbuseFilterAvailableActions[] = 'block';
...
}

But I am worried that it might affect the global abuse filter system as well as local Meta filters. Chris?

Correct, it would be available as a global action, as well as locally to meta.

I trust that the stewards wouldn't add a global rule that blocked, unless there was very good reason for it.

With the global filter in testing-only mode at this time, it probably would be fine.

However, in the long run, we can only hope for the global filter to be deployed across all wikis if we separate the global abuse filter settings from local. It appears to be the community's opinion that the global abuse filter should never be able to do restricted actions like blocking.

Whether global filters should block can be decided later, when a policy about global abusefilters is made. And even if it's decided to not use the block function in global filters, stewards are hopefully trusted enough to simply not use it then.

OK, I suppose we can proceed with this, per MF-Warburg. Stewards are trusted/expected not to create global filters that use the "block" action, and this should be communicated to them somehow.

Change 79458 had a related patch set uploaded by TTO:
Enable "block" action for AbuseFilter on meta

https://gerrit.wikimedia.org/r/79458

(In reply to comment #5)

OK, I suppose we can proceed with this, per MF-Warburg. Stewards are
trusted/expected not to create global filters that use the "block" action,
and
this should be communicated to them somehow.

It has been discussed on the stewards' mailing list.

Change 79458 merged by jenkins-bot:
Enable "block" action for AbuseFilter on meta

https://gerrit.wikimedia.org/r/79458

Done.