I forgot there are actual quotes on itch.
There is something different going on here. I can't tell if it's a bug or working as designed
I don't know shit, but you might want to map mouse control onto a sphere, which still isn't straightforward since it's 2d plane to 3d sphere, and there will be some weirdness in the corners like there is currently but probably someone came up with a solution to that before. It should at least be easier to debug when you can display your controls as a sphere.
I'm hesitant to add more inertia because I think it will make it feel less like a bat and more like an airplane. But I would like to increase the speed overall. "Gliding" also to me feels like what an airplane does
Bats are just small planes until they flap their wings
I'd agree that inertia would make it hard to make the controls responsive and you can easily overdo it, but you can also think about this in another way: smoothing out the movement and allowing camera to do more work. Right now the camera and movement coordination feels stiff. I move my mouse and bat almost instantly heads to that direction, after some struggle. I just replayed it and noticed that the way you implement the controls is unusual because it's like camera itself feels affected by the bat rather than camera pointing direction for the bat to go to. Implementing some inertia or just smoothing the turns will allow you to do wider mouse movements to allow for tighter turns by overcompensating without spazzing out - right now it feels like I'm fighting against the bat rather than steering to the direction I want to go to.
Once you get this right implementing gliding physics will feel like a no brainer decision.