In addition to highlighting one or more lines in a GitHub link, you apparently can highlight from/to columns within those lines. I can't quite figure out how to do columns from the UI, but I somehow did it once accidentally.

Example from manually manipulating the URL: https://github.com/square/okhttp/blob/parent-3.14.9/okhttp/src/main/java/okhttp3/internal/platform/AndroidPlatform.java#L161C24-L164C24