How can I moderate the users that use the same name than the author of the post

I’m not sure I understand because you’re not being careful with your use of the word “post.” Are you saying that people comment on your blog using the post author’s name? Are are you saying that people post to your blog using the site administrator’s name?

I’m going to assume you mean “comment” and not post because the user would have to have an account to post an actual post on your blog and in that case you could easily set their level so they couldn’t write posts.

As far as stopping people commenting using your blog owner’s name, I don’t really know of anything that can stop a person from using whatever name they want. (There might be something, though, and if so I’m sure another person will reply to correct me.) But you can force commenters to need to be registered to comment. They can still have the same display name as the blog author, but you can easily show the difference between a commenter and your blog owner if that’s the case.

There are also some styling things you can do that format your comments so people can visiually see this commenter isn’t the blog owner — enabling gravatars, for instance.

Sorry, I wanted to say “comment”, no “post”.
Ceo says that I can easily show the difference between a commenter and the blog owner, and I like this idea.
How could I do that?
Thank you very much.

CSS styling, I found this to be a good starting point.

OK, thanks a lot.