25.13.2 Hard and Soft Newlines

In Enriched mode, Emacs distinguishes between two different kinds of newlines, hard newlines and soft newlines. You can also enable or disable this feature in other buffers, by typing M-x use-hard-newlines.

Hard newlines are used to separate paragraphs, or anywhere there needs to be a line break regardless of how the text is filled; soft newlines are used for filling. The <RET> (newline) and C-o (open-line) commands insert hard newlines. The fill commands, including Auto Fill (see Auto Fill), insert only soft newlines and delete only soft newlines, leaving hard newlines alone.

Thus, when editing with Enriched mode, you should not use <RET> or C-o to break lines in the middle of filled paragraphs. Use Auto Fill mode or explicit fill commands (see Fill Commands) instead. Use <RET> or C-o where line breaks should always remain, such as in tables and lists. For such lines, you may also want to set the justification style to unfilled (see Enriched Justification).