Thanks. To clarify, I wasn't asking you to replace them with trivial challenges, but rather simply challenges that the player can see upfront. Like I said before, you have to be very careful when introducing and building upon invisible blocks, to the point where you basically have to design the whole game around them and use them frequently in order for them to be intuitive and fair, especially if you're gonna use them without hints. Not even Lost Levels could pull that off perfectly, so don't feel too down about it.
One example of a potential replacement could be: for Load-Bearing Grid's first painting, below the bottom jump-through platform in that shaft, add one extra jump-through platform that can only be reached by jumping from the item block. Then, you could add a spike on the left side of the new jump-through block so that a simple running-jump wouldn't be enough, and the player would also have to slow down at the right time to land safely. That should be non-trivial enough for world 3, don't you think?
EDIT: Oh, and just in case this also needs to be specified, the shopkeeper sometimes calls the name of his store something like "Jason's powerups" or "Jason's quality powerups," which would require the p and q to be capitalized (watch your p's and q's! ;P). I guess it could be one of those slogans where the name of the store is just "Jason's" followed by listing one or two things the store sells, but then there'd at least need to be a comma after Jason's.
EDIT 2: Discovered another Hikkori Skull glitch: if you run into a wall while phasing, you can reliably phase again in another direction. I guess you won't fix this one since you said you're okay if something's unfair in the player's favor, so maybe keep this in mind for the sequel since it lets you expand on it by allowing for makeshift wall-jumping.
EDIT 3: Okay, okay, get this: I noticed a couple grammar mistakes while rereading the 1.0.8 launch post. In the first paragraph, you say "flaws that's been" instead of "flaws that've been," and in the second paragraph, you say "these changes trends towards" even though a plural noun (changes) means the verb (trend) should not have the added s at the end. ^__^ EDIT 4: ...and on that same topic, I just noticed that the store's description of the Blood Violet says "enemies that loves" instead of "enemies that love"