I believe we're already past that point. Search for the term "reputation management". Some companies ARE willing to pay money to rebut a negative viewpoint with a human voice, and Reddit is by no means immune to this.

I don't think the question should be "if" it is happening, but how far some companies go (behind-the-scenes) to use human voices not only defend but advance their position.

They've definitely caught on. Depending on the community, lots of bots are appearing to shill for specific brands, some better than others. Example: /r/malelivingspace has a big interest in Eames Lounge Chairs, and every time they get mentioned, a few new accounts pop up like clockwork to say how much they love their specific brand censored replica lounger. A ton of other random sites get these astroturf responses too, if they talk about it.

The worst part is that if they were a bit more skilled about it, it would be indistinguishable from an actual recommendation. Give it another few years.