Well, my point was that what they have in common is the conversation, shared diegetic space, and to add an item, avatars through which the players frame their end of the conversation and their imagination of exploring the setting. That's all fall more fundamental to RPG play than what we are here calling playstyle.I can't see the post you are responding to so apologies if I'm missing something. I've been increasingly feeling over the past year or so that narrative and trad games are entirely different games, though.
That's subjective and qualitative and so could be argued about forever. So all I'll say is that there does seem to me to be such a large qualitative difference that people who like one very commonly do not like the other because it breaks core assumptions about what gameplay is and what they want it to achieve.
That seems sufficient to me to draw a hard boundary rather than a soft one. Even if they may both be RPGs, in the way soccer and baseball are both sports.
I think your hard lines project will fall well short of satisfaction once it encounters the whole plethora of games that combine elements of the two. This is why I said that the term narrative, for example, is probably more useful to describe various aspects of a given game than it is the game itself. I think the question might be better put 'how narrative is game X' as opposed to 'is game X narrative'. The former provides a whole lot of useful discussion space, while the latter almost immediately runs into problems.

