Dear Geshe-la,
It would be interesting if you could give your view about the subject being discussed in the "DSh and other schools of Buddhism".
In this website you will notice that we try very hard not to fall in non virtuous speech, to say the least. People here are exceedingly considerate with one another and this is one of the beauties of this website.
Now, if you go to that particular discussion you will see that one of the members declares that it is perfectly OK to mix traditions and teachings, once one is a skillful practitioner. Our friend Alexis tried the best he could to defend our traditional Gelugpa view, that one does never mix traditions, and he gives very good reasons. But in the end, in order not to upset the other party, or in order to show his respect for him, he just leaves the matter open.
Since this is such a serious, "heart of the matter" question, I do not think we should allow newcomers to this site to think that yes, it is OK to do that, to start practicing all the traditions we are tempted to.
Could you add some of your Geshe knowledge to this discussion, please?
Particularly, to add more to the already excellent reasons given, why Dzogchen is contradictory with the teachings of our lineage ...
And particularly too, to add more to the already excellent reasons given copiously in this website, why it is not good to mix traditions.
Thank you for any answer you can give.