Thank you for amazing feedback! About Shiori's boss sprite - we don't really know what causes this problem, but it doesn't appear like that every time, only sometimes. We had some problems with her spritesheet during development but in our final rounds of testing everything was fine about her. You are only third person to encounter this issue and I assure you that we're currently looking for a way to resolve that.
In terms of platforming, we already have a solution for the headbumping on platforms issue (in next update you'll be able to pass trough them from below) and we are commited to make game easier to navigate trough. Particles will be replaced with floating ink bubbles of various colorations and platforms will be marked by animated dripping ink to distinguish them from static background sprites.
Undeground stage will undergo some changes too. Your observation about ink pool is correct and we also find it frustrating so we'll find a way to make it more fair. Asides from that we'll also space out pipes better since currently they require difficult jumps or are too close to wall and easy to get stuck between.
Your feedback on combat is spot on and will be completely implemented in future build. Glad you liked the game and I hope you give it a try once we polish it 100%!