I'd like to suggest a rule of thumb from the employer's/manager's side that I was given by a mentor once (and I've seen the consequences anecdotally both when I followed it and when I didn't);

Just like the article suggests not to accept a counter offer I'd say don't ever GIVE a counter offer (or try to keep the employee resigning).

Of course always treat your people well and try your best to resolve issues and keep on top of their aspirations and desires but when they've already made up their mind to resign and they actually resign rarely (in my limited experience) can anything good come from you persuading them to stay because:

A) they'll likely leave anyway within 1-1.5 years B) they might never actually have left and they're using very poor/immoral negotiation tactics C) it sends a horrible sign to the other employees saying they (only) get ahead if they threaten to resign

And you have to be pretty fil with whatever your convictions are here I believe. So in my view the article is right - never accept a counter offer (I did once and while it was a bit promotion it was a huge mistake) but also never give one!