Hi All – just testing to see if anyone is around. I;ll start trying to use this forum to communicate about all PIPish matters
Hi Theresa, I am around! 
Yes, the idea is indeed to use this forum for the PIP discussions. There is a category “Implementers Forum” with a subcategory for each PIP and another subcategory “General discussions” for, e.g., discussions of new PIP proposals, general Prolog language design or implementation issues, etc.
You should be getting these posts also by email. If not let me know, you may need to activate the categories you watch. One thing that does not work yet is being able to reply to those email messages and having the replies appear automatically in the forum. Should work soon though (it is being worked on right now).