Link from them doing this in 2010. I highly doubt it has slowed down or stopped.
https://www.youtube.com/watch?v=LofScCiJT4c
The question still remains, are corporations doing this actively/knowingly or is it only governments that are doing the shilling.
As for paid shills, there is an entire sub-industry of PR called "Reputation management" devoted to this.
(I don’t have a direct link to said FT article, just a photo I took of said military person’s quote which is somewhere on one of my computers)
Sure. But there are also fanboys everywhere. Between presumption of good faith, Occam's Razor, Hanlon's Razor, and the breadth and depth of fanboyism I've seen online, my default presumption is always "fanboy" over "shill". Similar to your point about nationalists.
As for tech companies, I would honestly mark a lot of that down to fanboyism. Not that I'd be entirely surprised, but I somewhat doubt that Elon Musk, in particular, is actually paying all of those people. And Tesla seems to have the most defensive supporters on the internet. People talk about Facebook and Google for their privacy practices, Apple for their crappy laptop keyboards, but it's a tiny minority that goes after Tesla when they're the company least capable of hiring people to argue on the internet.
(I would also assume that it's a little bit overrated how often this happens, for the sole reason that I spend a lot of time arguing on the internet and never once have I received an offer to go pro!)