That's just going to result in people committing unused vars to their repos. People are already doing that now after adding '_'s by hand. https://news.ycombinator.com/item?id=32753079 It's going to get even more common when underscores are automatically added all over your project without user input and you have no chance of remembering where they all were.

If the goal of not having warnings is to increase code quality, it's actually doing the opposite.

I don't understand this insistence on working around the problem by layering on tooling, instead of just fixing the problem to begin with.