"sharer of misseries with his troops" strikes me as being a bit of an overstatement. The troops marched on foot, scavenged for food, and slept in open bivouacs. But Napoleon, for reasons of image and also by virtue of being a very focused professional military type, had fairly humble personal requirements and he shared the same hardships as other officers to a larger degree than many (perhaps most) of the higher ranking and typically noble officers in other armies in the earlier campaigns, although I sense that his personal camp became a bit more lavish in the later campaigns. He certainly has more claim to sharing hardships than any other contemporary head of state. Duffy provides quite a bit of information on Suvorov that seems to place him in a similar category with Napoleon - again this may be a matter of Suvorov promoting an image or just the habits of a professional military man who doesn't need fluff. Suvorov was regarded as odd. Buxhowden was notorious for travelling in style with an extensive personal baggage train. Massena brought his luxuries with him to Portugal (lots of wine and his mistress, presumably the essentials of life for him) but was still travelling light by comparison. I don't have any sense of the hardships endured by the Bennigsens, Bagrations, Schwarzenbergs, Bluchers, etc. to know to what degree these army commanders shared the hardships of their lower-ranking officers.
In the case of N leaving Russia, given the continued retreat of Murat and then Eugene to its ultimate position behind the Elbe in the face of a struggling Russian army, I do have to wonder if a bold Napoleonic presence might have held Kutusov at bay somewhere east of the Vistula - or at least east of the Oder - and prevented the full participation of Prussia in the next act. The destruction of a pursuing Russian army or Yorck's "renegade" corps, for example, might have had as much effect in Paris as Napoleon's presence and certainly would have had more effect in Berlin. Napoleon definitely wanted Murat and Eugene to make their stand further east, but I'm not sure how practical this desire was under the circumstances.
I think, though, for a commanding officer to leave a command that he can no longer do anything for (leaving it in the hands of a responsible subordinate) taking maybe a handful of troops with him and going elsewhere to work on raising an army that will be used to extend the war against the enemy is a valid reason for "abandoning" the army. Extreme circumstances demand unconventional methods and if the commander's presence elsewhere can do more to further the war effort (this is the part is open to debate then and now, but this can be reasonably accepted as his belief) then the greater value has to be considered as valid justification - even if the action would be unthinkable if the army he was leaving was capable of prosecuting active operations against the enemy.