Just a few examples:
Many projects link their GitHub namespace with other services like CIs, Linters, Test Badges, Doc Generators and so on. They usually treat URLs case-sensitively, which now leads to broken references. Try to click the build badge on one of their own projects, and see where it takes you: https://github.com/microsoft/vscode-go
Some build systems will fail as they check out dependencies including the full canonical namespace, and now can't find the uppercase version in the filesystem.