SUMMARY
It seems like most brush engines have problems in regards to either tiny strokes or point-dabs. This is annoying when working with pixel art, working in high zoom levels, and/or when you want to create very tiny strokes in general.

The following brush engines do not generate dabs if a stroke is less than half a raster pixel (or less than one full raster pixel, in the case of color smudge engine):
* Pixel
* Color Smudge (regardless of algorithm)
* Quick Brush
* Spray
* Hatching
* Grid
* Clone
* Deform
* Tangent Normal
* Filter
* Mypaint 
The above engines are capable of point-dabs, though. I define a point-dab being as simply clicking on the canvas, without any drag.

The following brush engines can't do point-dabs:
* Color Smudge (regardless of algorithm)
* Bristle
* Shape
* Curve

STEPS TO REPRODUCE
1. Zoom in to 6400% or higher.
2. With a Pixel brush, make a stoke smaller than half a raster pixel.

OBSERVED RESULT
No dabs are created.

EXPECTED RESULT
There should be at least one dab.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Debian sid
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.98.0
Qt Version: 5.12.12 (appimage)