This is an impressive game with sadistic stage design and marvelously malevolent game mechanics. There's a reason your game made it to the first page, and it is ingrained within pure challenge and learning curve that could only be conceived by a game designer for game designers. I'll go over what i like and aspects worth improving upon to tailor the game to a larger demographic; all this, while making suggestions to preserve its difficulty level after modifications if I get to that.
The 'crippled' mechanics were too sluggish for my taste, but unlike me, plenty of your audience members (young adolescents and kids who don't follow Newground's age ratings) may run out of patience and quit the game entirely before seeing all that it has to offer. I suggest increasing the character speed by a few more pixels per second so the audience's attention span does not expire due to a lack of activity at first. The difficulty here stays the same regardless of the recommended change and I like the difficulty level here very much (where else can I choose the wrong spellcaster to teleport me into a pit of lava, that's awesome)
The 'illiterate' mode mechanics serve as the basic template for understanding the the stage design and how to navigate it. It does not appear to have any other purpose than that, but that does not mean it does not have any worth, it might be my favorite stage because it taught me so much. This stage requires no modification and I have no recommendations.
The 'spastic' mode mechanics can get very annoying; I'll be honest that gave me a hard time since there was no ability to predict when the 'spasms' would occur. I recommend two crucial changes to this mode. The first is the mechanics behavior; instead having your code generate random movements in a single uniform direction for long lengths of time, modify the mechanic so the character randomly shakes, oscillates left and right, or jumps lightly; if that is not to your liking I suggest reducing the amount of time a random direction is locked in. The second change in the spasm mechanic I recommend adding to the game is to grant the player some priority in movement so they can combat spasms by allowing both commands (the game spasm command plus the player) to occur in a fashion that moves the character slowly in the desired direction; for example, if the game wants the character to move left, but the player can move right, the character can move slowly in the player's desired direction but slowly. The current spasm mechanics have deleterious effects on the game play of this mode. The normal time span of a random act or 'spasm' is too long to fight against in order to survive over or by lava, requiring more deaths than necessary. What's more the only way a player can fight a spasm currently while moving to the left, for example is, only by pressing the key to move right, which neutralizes all horizontal actions in some cases as long as 3.5 seconds if not more. Occasionally the spasm command locks up and the character continuously moves to the left, but never the right, which means walking back into a previous stage to die, only to re-spawn on the beginning side of the previous stage with the same command taking effect. This terrible process can repeat up to three times if player tries to fight it, but the player could backtrack as far as 6 stages if the player let the game take control of the character entirely with spasms. Most people would rage quit in the early stages of this game mode, but I managed to find a cheaty exit through a jumping spasm along the way and used the discovery to circumnavigate the second half of the map. I'm not sure if that's an Easter egg or not, but it definitely is the ace in the hole that makes this mode playable
The final game mode of near blindness is impossible to play on the first try. I only got as far as I did since I played all the previous modes before this one and memorized the stage layouts. Having only a limited scope to see in by blacking out the whole stage aside from a radius around the character, equal to the character's height, makes it impossible to even use trial and error on some stages since it's hard to gauge which platforms spawn where and how far away they spawn. The only solution to this is to change the mechanic so everything is not blotted out in darkness, but instead blurred and pixelated like my distance vision in real life, but even that would not be enough to play this mode all the way through if I played that mode first instead of the others. It is hypothetically possible to use the secret exit I found to circumnavigate the map, but not a lot of people know about it.
All in all its a crazy game worthy of its position on the first page. I can see why this game has plenty of potential but I also see there is much more to be desired. Just remember to never give up. Lastly, remember that artistically speaking, your original concept art or brain child might be your darling, but whether it is or not, it's okay if we murder our artistic darlings by completely changing key aspects of their composition.