Aviquill's canvas has two kinds of visuals living on it at once, and it took me a while to admit they're not the same thing and shouldn't be designed the same way.
The ambient layer
Rain drifting down the background. A slow aurora wash. Particles drifting past at the edge of your vision. These are the canvas effects you toggle on from settings — there entirely to make a blank workspace feel less like a blank workspace. Turn them all off and nothing about how Aviquill works changes. Turn them all on and nothing about how it works changes either. That's the test for decoration: you can delete it and lose nothing but atmosphere.
I still think that atmosphere matters. A canvas you're going to stare at for hours a day shouldn't feel like an empty hospital room by default. But it has to stay optional, and it has to stay quiet enough that it never competes with the actual content for attention. If an effect makes you notice it before you notice your notes, it's tuned wrong.
The functional layer
Then there's the nebula-style glow around a group, with bracketed corners marking where it starts and ends. The thread lines drawn between connected blocks. The thickening marks on the ruler over a dense cluster. None of that is there to look nice. Delete it and you lose real information — which blocks belong together, which ideas depend on each other, where the dense parts of your canvas are. These aren't effects you can toggle off, because turning them off doesn't simplify the canvas, it just hides the structure that was already there.
That's the line I actually use: if removing a visual loses you information about your own canvas, it's function and it stays on. If removing it only makes the room quieter, it's decoration and it's your call.
Why the line matters
It would be easy to lump all of this under one settings toggle — "fancy visuals: on/off" — and call it a day. I didn't, because a user who turns off the ambient rain shouldn't accidentally also turn off the thing that tells them which blocks are grouped together. Those are different categories of pixels doing different jobs, even though they can sit a few inches apart on the same screen.
Every time I'm tempted to add a new visual flourish, this is the question that decides which bucket it goes in — and whether it gets a settings toggle at all.