Placement of "en" in conversational past

Question

In this lesson the note about the conversational past states that in these cases, the en will be before or after être: formally, it should be before, but in practice, it often ends up after.

Following this advice I put "Nous en nous sommes allés après le dessert.". This was flagged as incorrect, and "Nous nous en sommes allés après le dessert." as being correct.

This seems inconsistent with the note. I see there have been other questions about this topic. To me, "nous en nous sommes" flows off the tongue better than "nous nous en sommes".

Accepted Answer

Patrick , the ‘choice’ is between ‘nous nous en sommes allés’ (more common in formal writing) and ‘nous nous sommes en allés’ (more common in speech).
Neither fits the word order you have used, which does not flow off the tongue better to native speakers. 
Worth looking again at the section on ‘s’en aller’ - perhaps it could be made more explicit by saying ‘directly before or after être’, but the examples do show both acceptable versions.
 https://progress.lawlessfrench.com/revision/grammar/s-en-aller-means-to-leave

Answer

Bonjour Patrick,
Maarten is correct! I've also acted on his great suggestion and amended the examples to highlight the position of "en" in this part of the lesson.
I hope this is helpful.
Bonne journée !

Answer

@Maarten, Doh! Obvious when you point it out, thanks! @Celine - thanks!