By "paragraph markers" you mean you wrap your text in <p></p>?
Blogger uses a wysislwyg (what you see is somewhat like what you get) editor. If you enter <p></p> in Compost mode, they will disappear on publishing.
If you enter <p></p> in Edit Html and switch to Compose, <p></p> will be lost. That includes a later edit when you open the post for editing and the editor is already in Compost (the editor starts in the last Published mode.)
If you turn Compose off and do all of your work in Edit Html, <p></p> and all other code you enter will be retained. That's one of the reasons I have Compost turned off, write in a text editor, do the markup myself, paste completed posts into Edit Html.
