@Everyone posting, "MK has no bad match-ups! They're 50:50 at best!"
1) Those match-up numbers are suggestive numbers
2) I'm almost certain that most people who say that don't main all of the characters who MK is questionable with, so there's no way that they know the actual match-up for each of them instead of just the questionable number.
3) Even if at best, each of them were 50:50, 50:50 still means it's a winnable match-up. Very winnable. AKA not banworthy.
Now lets see.
MK has no bad stages! Well, Snake, Wario, and Diddy also have no bad stages (when people say Diddy is bad on Norfair and RC I kind of lol). Should we ban them too?
MK has no bad match-ups! I already kind of covered this point. Plus, Snake and Wario only have 1-2 match-ups that are 55:45 or 60:40. Arguably, MK has those match-ups too.
MK over-centralizes the metagame! How, exactly? All you have to do is learn the match-up well, and you're set. You don't see character boards with each thread being, "Zomg MKs Dtilt, how do we beat it?!?"
MK places well at top tourneys! So far I've only seen one with any concern in it, and that's HOBO11 (and apparently those results are kind of skewed too because some people only used MK for one match-up, and apparently Hylian didn't use MK at all and it was placed by his name).
Cot4 had an MK (M2K, who by the way is easily the best at this game), a Snake, an MK, MK, and Diddy. That isn't bad. WHOBO results were skewed because again, we have M2K, the best at the game, three other people in the top who used MK only a couple of games, and generally most pro MKs came to this, but not pros of other characters like Anther, Ally, ADHD, and NL who would have all placed considerably well.
This might change when Genesis comes along and we look at the placements there. If like top 8 are all straight MK, yeah, that's going to be valid concern. However, I highly doubt that, and you can't ban something for a just in-case thing.
If we ban MK, then there will be more character diversity! This is obvious. If you ban ANY character, the mains of that character all have to switch to someone else, which means more diversity in tournaments. However, more diversity isn't a valid excuse to ban something. In most other competitive games, you'll realize that in top tourneys, you'll generally see the top 3 characters placing.
There is no true reason to ban MK at this point. He's beatable, and the match-ups are debatable and subjective. The fact that he has even close match-ups means that he's not even broken. He generally wins tournaments (except in the Midwest, lol), but he doesn't completely dominate them. He doesn't overcentralize the metagame.
I don't see the reason for banning MK other than, "I want it easier for my character to place well!" which is just a completely inane reason. You don't ban things to make it easier.