To have three different effects which sound like they should all do the same thing is confusing and inconsistent. Cleanse being diferent might be understandable, because it's a summoner spell. However Mikael's and QSS are items, so for the sake of consistency they should act the same. Mikael's could even build out of QSS as an MR item.
I assume because of how powerful Mikael's vs QSS is. QSS can cleanse anything, but you have to take up an entire item slot in your build as a damage dealer to make use of it. Mikael's is less powerful, but allows a support to give a great heal and remove most CC's on a champion. It does not cleanse the same things (such as suppression, removing Zed's ult, etc.) because that would allow adcs to never need a trade off of QSS vs another damage item as their support will already buy a QSS for them.
I agree that there's a lot of inconsistency to cleanse effects, which isn't good, but at the same time I think unifying them might also create issues of its own: 
is weaker than 
because it's basically an additional cleanse for the marksman, and making its active equal to QSS would remove the incentive for them to build 
, already a difficult purchase that doesn't fit into most standard builds. I think 
could afford to be updated to be equal to QSS, since it taking up a summoner spell slot is costly enough, and it was only meant to ignore some effects (suppression in particular) because of how hard it could counter some kits (
's full combo is still hard-countered by QSS even today).
Farther down the line, I think it would be better if Riot took a look at cleanse effects in general and set a clear plan with what they want to do with them in the future, even if it's a long ways off. I personally dislike them, because they allow you to nullify great plays at the press of a button and tend to hard-counter some champions (Malz in particular, but also 
and 
, who suffer even more than they usually do whenever Mikael's is a must-pick on every support). On the flipside, there are also some champions who would be completely broken if cleanses no longer were an option (Malz again, but also 
and any champion with long-ranged point-and-click hard crowd control), so there would be a lot of adjusting to do either way.
I'd be a-okay with Mikael's building out of QSS, though I'm hesitant about giving it MR greater than 60, so I don't think it be allowed to build out of Chalice.
Honestly, I would just change to have them affect everything the greatest one affects. Or if they don't, change what they call them. Something like: "Lesser Cleanse" "Cleanse" "Greater Cleanse"
To limit how easy it is to counter Suppression and debuff ultimates.
Only one thing exists which counters suppression, and it gets extended use for debuffs to make it more overall usable.
Mikaels is intended as a supportive, if it was as strong as QSS it would be far too strong on a support.
Cleanse is there in case you need a CC break during early/mid game where you can't validly have picked up the other two, but doesn't completely eliminate the threat of Suppression ultimates.
However Mikael's and QSS are items, so for the sake of consistency they should act the same. Mikael's could even build out of QSS as an MR item.
Riot's already stated a while back that they want to change up the active of Mikeal's or remove it from the game because of how hard it is to use effectively. Most players struggle to use it against most short/medium duration CCs (up to around 1.5 seconds) as it's hard to cleanse the CC early enough for it to matter. Any amount of ping you have can make this issue even worse.
Not saying that they shouldn't be consistent, just that it's probably not worth thinking too much about since Mikeal's might not exist too much longer.
I thought this was a thread about the different particle effects at first >.>
On topic, the logic that Mikael's and QSS are both items, so they should both have the same effect is sketchy. I can't think of any other items that do have the same effect. Many are similar, like Talisman of Ascension and Righteous Glory, but items generally have different effects, not the same effect.
