I don't play commander much so I figure complaining about it in that format is just like saying the sun is to bright, why can't they make better sunglasses.
I don't play legacy or modern, in part due to my poorness, in part due to lack of interest. Well it is probably because I am more interested in EDH. If I had the money, I would love to build a modern deck and show up to my LGS with it. Same goes for legacy. I would love to try them both, but I would rather put my money into EDH since I don't have enough to split it. Whatever my reasoning, I don't play the format, so I don't have an opinion about KCI or Eldrazi Winter. I hear about KCI not being healthy for the format, sure. Eldrazi winter wasn't too healthy for the format. However I never told anyone they were wrong for complaining about one thing or the other because I didn't (and still don't) have enough information on the subject.
If they make emblem interaction cards, I don't see how it will affect your modern or legacy play because as you said you can already deal with them efficiently. Either you have an answer and you win or you don't and you lose. Personally I thought walkers and emblems were too slow for those two formats, but again I don't play them, so I am not 100% on them. In commander an emblem stagnates a lot more than in modern. Say you have your 5/3
juggernaut and you get an emblem locking your opponents out of the game. In most cases in modern that shouldn't be more than 4 attacks. In commander that is 8 attacks to kill a single person. Then three opponents. That is 24 turns. This isn't a realistic version of a commander game, but I want to emphasize that the board presence you have in modern isn't equivalent to the board presence you have in EDH. I said it wasn't realistic representation of a commander game, it was an oversimplification to illustrate my point.
What is the difference to any combo-deck? some time you're faster (or resilient or whatever) than the combo, sometimes not.
The difference, at least in my experience is that combos usually close the game. Infinite damage to everyone, infinite hasty tokens, etc. A plansewalker emblem usually gives one person an EXTREME advantage to the point that it is no fun to play against, but it doesn't actually win the game for them. Most often the games end by everyone scooping because we are tired of waiting for the superfriends deck to find a way to actually kill us.
This M20 Chandra, potentially emblems each turn ... it looks very strong. but this is just 1 dmg each turn per emblem. in my opinion lot of average decks could handle it.
Your capitalization is giving me anxiety.
Remember when Chandra gives everyone their emblems, she goes up to 8 loyalty. That is a lot. Depending on the board state, she might not be going anywhere for a while, but even 1 more activation can be deadly.
Think of
underworld dreams and
howling mine. Depending on the format, you either need to chip away at 20 or 40 life, and 40 is definately a lot, but after a few turns, combined with shocklands, fetches, etc. it adds up. Albeit you cannot increase the damage of the emblems like you can with
underworld dreams. Usually that card will be played in conjunction with Nekusar and wheel effects.