In fact, this MR does not completely fix the dotted line problem of small size brushes (such as 0.2px).
And, if you look closely, you’ll find that the small size brushes have unnatural shades of color.
[5.1.0-prealpha]Painting very thin lines will become dashed - Develop / Artists Feedback & Testing - Krita Artists (krita-artists.org)
So I also hope that there is a way to completely solve this bug without affecting the pixel brush.