Have you ever modified a commit message after completing it in Git?

Yes, in Git you can change the message of the last commit using the command:

git commit --amend -m "New commit message"

This will change the message of the last commit while preserving its content.

If the commit has already been pushed to a remote repository, after changing the message, you need to perform a force push:

git push --force

However, be cautious with --force, as it can cause issues for other developers working with this repository.