Likely not what's being discussed in the article here, but I used to be active on a developer mailing list where discussion of pricing/hourly rates/etc. was for

Likely not what's being discussed in the article here, but I used to be active on a developer mailing list where discussion of pricing/hourly rates/etc. was forbidden because there were a lot of contractors/freelancers working in relatively narrow spaces and some jurisdictions could consider it a form of price fixing. Essentially, imagine if all the experts on some particular niche technology sat down and said "we all are going to charge at least $X/hour". Doing that explicitly is illegal. And in a forum related to some profession, having conversations about "how much should I charge for X?" or "how much do you all charge for X?" can quickly run into legal grey areas. Discussing salary probably is safe (but IANAL) but you do have to be careful if it's a conversation about rates happening between competitors in a market.