Editing the git commit message in GitHub

Is there any way of online editing the commit message in GitHub.com, after submission?

From the command line, one can do

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

as correctly suggested in another question.

Trying git pull and then git push has worked (without any other commit having interfered in the mean time).

But can it be done via the GitHub website?

GitHub's instructions for doing this:

1. On the command line, navigate to the repository that contains the commit you want to amend.
2. Type git commit --amend and press Enter.
3. In your text editor, edit the commit message and save the commit.
4. Use the git push --force example-branch command to force push over the old commit.

Source: https://help.github.com/articles/changing-a-commit-message/

No, this is not directly possible. The hash for every Git commit is also calculated based on the commit message. When you change the commit message, you change the commit hash. If you want to push that commit, you have to force that push (git push -f). But if already someone pulled your old commit and started a work based on that commit, they would have to rebase their work onto your new commit.