You can remove a paragraph by deleting all the text in the paragraph or by dragging it to some unwanted place.
Remove by Editing
Saving an empty paragraph is recognized as a request to delete the paragraph. This action shows up in the journal as r for remove.
Some other story item types can be removed in a similar way. For example, removing the caption of an image removes the whole image item.
Remove by Dragging
You can remove any item by dragging it to an unwanted page. Perhaps you have an unwanted page called Trash. Drag unwanted items there and they will be out of your way.
Some items, such as unwanted Data items can only be removed this way.
You can use any page, including the Welcome Visitors page, as a temporary Trash. Empty this trash by calling up the penultimate action in the Welcome Visitor's journal then fork this version back over your "trashed" version.
You can add a reference to Trash to your home page. Use Shift-Click to open it beside anything you might be editing.
You can open a page called Trash by adding the characters /view/trash to the URL in your browser's location bar. Press return to reload all visible wiki pages along with the new Trash page.