Related to T194125, T196092, and discussion on IRC. This experimental setting controls passing SET NAMES=utf8 on connection, which isn't recommended if you're using the binary charset (what we're standardizing on).
We should remove this option from the installer, and then remove it from MediaWiki core. This has very clearly been marked as experimental, and doesn't need a deprecation period.
- Remove from CLI installer for new installs (was never exposed via web installer). – MediaWiki 1.31
- Deprecate the configuration variable. – MediaWiki 1.31
- Remove the configuration variable. – MediaWiki 1.33
- Remove the option from the rdbms library.