Is it possible to have the same card but from two different editions in Commander? For example, the planeswalker Jace Beleren.
The printing, set, art, and as of Unstable even the stats and contents of the text box all are not relevant for determining if there are too many of that card in that deck. The only thing that matters is the English name. As of a recent rules change you can have different Jace's in play at the same time, and of course you can have them in your deck due to having different names.
The only cards exempt from the card limit are cards with the supertype basic (the 11 basic lands by name, 5 snow covered, 5 normal and Wastes), Relentless Rats, Rat Colony, and Shadowborn Apostle. All other cards can have 4 copies in a constructed deck and 1 copy in an EDH/Commander deck based on English name. (As long as the card is legal in that format and has not been restricted to 1 copy in that format)