> someone at HR is already looking into replacing you.
Well, not that I disagree that accepting a counter offer is a bad idea, I'm pretty sure that someone at HR is always looking into replacing you, all the time.
I don't think that hr is looking to replace people, because it's way too hard to hire. At my company every new hire looks like a magical lucky serendipitous event. Hiring is just that hard. HR grudlingly matches people's other offers. They are too exhausted to look for someone to replace their existing employees.