If you are an admin to any page, this extension will give you an ability to comment on behalf of that page under any post in your news feed.
After you install the extension, on www.linkedin.com you will see an extra comment button next to the regular comment button.
By Clicking it you will be navigated to the post details page and you will be able to comment on behalf of the page you are managing.
Feel free to reach out if you have a feature request or comments.