clearly said my Mook...
if you nested even with same origin and destination, if it is not against the min.stay rule, it is ok. (I nested a N-fare with not min. stay requirement and perfectly fine)

If your nested pairs are of different origin and destination, (A-b-A, b-C-b), it is ok as well since you are just doing a "side trip" but not returning to origin.

Just thinking that if you are not violating the fare rule, you should be fine.