As you have seen, MSE allows you to make comments and publish posts directly from the browser.
Whether or not these comments are eventually acquired by MSE depends on your search topics.
For Facebook pages, your comments should automatically be acquired because a Facebook search topic will by default acquire all posts and comments for a page.
For a Twitter search rule, your comment may or may not be acquired... If you configured the Twitter rule to acquire all Replies, then your reply should be acquired. If you are not acquiring Replies then you probably won't see your comment be acquired.
For a keyword search rule, for example for the keyword "#dynamics" then your comment probably won't be acquired. If you acquire a tweet that contains #dynamics and then reply to that tweet. then it depends on what you wrote. If your reply contains #dynamics then it will be acquired, otherwise not.
What exactly is your scenario? Perhaps I can offer a little more concrete clarification.
