I've lived all my life under the assumption that every keystroke I make is recorded and every word I say, too. And honestly I think that's closer to the truth than the naive opposite assumption. Be it corporations or governments. That war has been lost long ago.
I don't understand why should I care that an AI model is being trained on Reddit text. So what? It's all out there for anyone to read; if I didn't want people reading what I wrote, I wouldn't have written it. What difference should it make if that someone happens to be a robot?
Quite frankly, I'd much rather write a little script that keeps posting some AI comments to contribute to their dataset, but make it basically unusable