Summary: I'm just gonna take what I wrote in my r/krita thread.

This is for the inner glow effect. When I use the effect with a gradient that I've made, not the default provided ones, a weird almost halo affect displays over the entire image. The effect is not erasable and is entirely connected with the layer style, as in if I disable it or hide the layer, the effect goes away.



If you'd like to replicate, here is how to replicate it.

 1. New Document, mine was a 2048x2048 sheet, with all default values.

 2. Draw a selection of any size or shape, and fill it in with a color, I used #909090 for this example.

 3. Go to Layer>Layer Styles and enable inner glow and then go to it's settings.

 4. These are the values for all the fields, excluding the gradient, which I'll get to:
Addition (Note this effect happened with all blend modes that I tried)
100
0
Softer
Edge
0
146 px
100
0

 5. For the gradient, create a new one and change the far left color to 505050 and the far left to 909090 with .5 opacity.

When you select the gradient, a weird grey halo will appear on the white background of the image surrounding the effected area, which is non erasable.

However, this effect is sort of lost when you merge the layer downward and then erase the effected areas, however this makes using the effect very impractical.


SOFTWARE/OS VERSIONS
Windows: Windows 10 Professional
Krita Version: Appeared in 4.1.7, 4.2.1, and 4.2.2