koobas.hobune.stream
Problem is not reproducible or outdated
Text in custom editor is displayed/rendered with boxes around characters...
It's not about UIElements, I am using the older UI system. And I have a feeling that I encountered the same issue at some point before, but I don't remember how I solved it. It all happened just out the blue and I can not figure out what's causing it.
Also, it can change text in other tabs, like so: 
Turns out that for whatever reason the following two lines of code were causing the problem:
EditorUtility.SetDirty(list);
AssetDatabase.SaveAssets();
These were called with OnGUI() method, but I moved 'em and now they are only called when a value in the list is changed. It must be noted that I do have a huge list (800+) of items, so I think that probably saving the asset each OnGUI() call was not the best idea ever lol.
Hard to tell without seeing any code, however it looks like you somehow changed the rendering material / shader. Did you at any time call SetPass of a material somewhere in your code? Maybe you used other methods which aren't part of the IMGUI system which may have changed the active material / pass. It looks like some sort of wireframe / outline shader.
Thanks for your reply. It turned out that for whatever reason the following two lines of code were causing the problem:
EditorUtility.SetDirty(list);
AssetDatabase.SaveAssets();
These were called with OnGUI() method, but I moved 'em and now they are only called when a value in the list is changed.
