Two options here:
- Add an onArticleParserOptions hook in DiscussionTools to set the useParsoid flag, or
- Add code to ParserMigration to allow turning it "on" by default for all users in a certain namespace (aka Talk)
We're leaning toward option (2) right now to keep the opt in/opt out logic in a single place. That would involve making a new "wgDTUsesParsoidByDefault" config option for ParserMigration and then turning this on for wikitech.