The r/PPC subreddit is a great place to find conversation about all types of PPC topics. The community has great group of 4 moderators that do a great job of filtering out any obvious spam or unrelated content. The community is a diverse group of experienced analysts and people just getting started on the PPC journey.
The community is not afraid to be opinionated. We found this out firsthand after a 'Ask Me Anything' in r/PPC this past March. Titled, "I am cofounder of a startup working on a growing PPC app, AMA" the post received some solid attention and was on the homepage for a few days. It was a great opportunity to talk about what we were working on at the time and where our platform was. We really enjoyed that it was an open forum to address a lot of tough questions and receive some kind words for the problems we are solving.
If you haven't before, checkout r/PPC.