It is not so. At least about 15 years ago I already used to get a reward for placing advertisement in my signature on some forums. It was a time when SEO links were very actual, so many were very motivated in advertising via pass-through links. It was different, because the amount of already left posts mattered and it was less important how active you are at the moment. But well, I was paid for advertisement in my signature. Of course there was no BTC at that moment, so we got the reward in USD and much less than projects pay for it at the moment. But I first found it much earlier than came on bitcointalk.org and even earlier than bitcointalk.org first appeared.