While it was certainly not encouraged, you'll note that undisclosed COI was not actually banned, just discouraged. There was extensive and widely advertised discussion in November 2013 [1] about three anti-COI rules, all three of which were shot down. This is not the first time it has come up, and it had repeatedly been shut down.
As for the WikiPR incident, the fact that they were banned has less to do, I imagine, with the fact that they were paid than the fact that they were essentially vandalizing Wikipedia. If they were getting paid to write neutral, balanced, well-sourced articles, I'm sure no one would have cared.
As for the WikiPR incident, the fact that they were banned has less to do, I imagine, with the fact that they were paid than the fact that they were essentially vandalizing Wikipedia. If they were getting paid to write neutral, balanced, well-sourced articles, I'm sure no one would have cared.
1. https://en.wikipedia.org/wiki/Wikipedia_talk:No_paid_advocac...