That's a great article, and I wish it reflected my own circumstances better.
I am both mum and stepmum. Both my DCs have (different) stepmums, one of which was the OW that signalled the end of the relationship (with exp). They are both good to my DCs and I am happy with that.
On the flip side, DSSs mum is a nightmare who never considers how her vitriol will affect her son. He is permanently stuck in the middle, sometimes manipulates situations as her and DS don't speak (can't without rowing), and DH hates her for it.
I know that my DCs are far more emotionally secure and stable as a consequence of how we've dealt with moving forward so even in the hardest circumstances, I'll always encourage splitting couples to put their DCs emotions above everything else that they feel.