Using them occasionally (very occasionally) in formal writing is ok. As soon as you use them more than once, they lose their impact. You would never use them in an email or any other kind of everyday writing. I tell my students I don't want them to use indeed or moreover at all. And when they use them in speaking, it's even worse!
In speaking, it's very rare to hear someone use words like indeed, moreover, therefore, consequently...When we speak, we use very few conjunctions; and, but, so, because.
We can use indeed in speaking, but we use it quite differently to how you use it in your essay-writing. Indeed means without any question.
For example: "Did you have a good time?" "Indeed."
We often use it after very. For example: "It's a very nice car indeed."
Or we can use it in a question to express surprise or doubt.
"I'm not going to do my homework tonight." "Are you indeed?"
So it's time to forget about indeed and moreover and concentrate on speaking naturally and not like a school textbook. Indeed.