That would be multiple uses of the <br> (line break) tag, either on its own or after the <p> (paragraph) tag. Ex:
Paragraph 1
I inserted 3 <br>'s between Paragraph 1 and this line of text.
I inserted 1 <p> and 1 <br> between the previous paragraph and this line.
One more thing; if you've invalidated the "HTML auto-detected" described in the help of each posting comment page, you'll also lose the ability to type a '<' or '&' at the beginning of a word without putting a space between it and the rest of the word, at least without resorting to some HTML "trickery".
To get the '<' followed immediately by more characters, type <(remainder of word with no space). To get the '&' followed immediately by more characters, type &(remainder of word with no space).