A few potential fixes (try separately, and then combined):
- Enable “Defer compression” (compression is processed after pretty much everything for the image)…perhaps it’s compressing the lines with thickness before they’re able to retain their initial level of detail
- Select a different setting than “UserInterface2D RGBA” next to the Compression Settings label
- Modify the Lossy Compression Amount and/or Compression Quality from Default
- Change “Power of Two Mode” to Power of Two (I saw this in a thread about using a program that was said to be compatible with exporting and importing to Unreal Engine, yet it was for the program’s export options…not Unreal’s import options)
- Change the Filter from “Nearest” to a different setting
There’s also “Force PVRTC4”, which is a different format that is utilized by graphics programs…but I’d remain wary of it for now. More of a last resort.