I totally agree with the first "I'll Take It" rule. I ran into complication selling some ham gear once where I was answering an "I'll take it pending the answer" first person when a second person "took it" before I could finish my reply to the first person. Everyone understanding that the first published, "I'll take it." wins eliminates a lot of refereeing.

So I now understand the person who said, "No PM counter offers" was stating personal preference, not "rules".