This emoticon has a white background instead of a transparent one:
Doesn’t work good with dark theme.
Found this if that helps 🫵 Index Pointing at the Viewer Emoji
//EDIT: higher resolution of same image (easier to clean up before resize) (//EDITception: no it is actually same file dimension, but still a slight difference)
🫵 <= emoticon from character (not really readable)
I’ve found one that you can’t even with dark mode on 
To me it is not really the same issue, here the image is correct, it is not just very visible because of the nature of the emoticon itself (dotted line face), hard to make it better, as the shape is defined with little dots, can’t think of a compromise that would work on dark and light theme, with the dotted shape or eyes/mouth.
Another one that is not really readable in dark mode:
