See https://discourse.phabricator-community.org/t/firehose-webhook-not-working-with-self-hosted-requestbin-instance/2240/. I want to make it easier to link to configuration from system text.
We currently use this weird hack with {{...}} that only works within Config itself. Instead, use @{config:...}, which is already used by Diviner for @{class:...}, etc., so it shouldn't conflict with anything.