As a man who's been married for 15+ years, I would absolutely advise young couples to consider the disciplines and policies they expect their relationship to abide by in much the same way managers and employees discuss their policies and procedures. "Talk freely", yes, but also, as this article so correctly points out, understand the effect your language has on your relationships (direct reports, friends, spouses, family members) and make sure to not treat heavyweight issues with an air of flippancy or triviality.
My wife and I decided, before we got married, that divorce was off the table for us. Understanding that it is not even an option for me (and trusting/believing my spouse that it's not an option for her) gives us so much stability to launch into uncomfortable topics and conversations with each other. If we got into a habit of treating that topic lightly, I could easily see many instances over the past decade where life has gotten hard, we would be in the middle of a stressful situation, and we would have doubted each other's commitment.
There's a broad range of experience out there in marriages, so it's likely possible to have that same stability while regularly joking about divorce, it just seems like a foolish thing to risk so huge a downside (actual divorce) for so little an upside (getting to joke about divorce).
Bringing this back to the article, that's the same idea at play. For the manager to restrain themselves from a few key topics which are inappropriate for them to joke about, they avoid a huge minefield of stressful issues for them and their direct reports.