Dreamwidth's original post editor and the reply editor (once you select "more options") offer a don't auto-format ticky box. (Can't find that control for new editor.)

In the HTML spec, newlines are supposed to be ignored. To make everyday writing easier, DW's editor respects newlines you type. That's why you get extra space when you separate the list items. When you check "don't auto-format," those newlines are ignored when posting.

The other thing auto-format provides is making totally plain links clickable. The HTML spec requires you to wrap a link: to create
https://example.com
you have to type
<a href="https://example.com">https://example.com</a>

Here's a bare link that the editor has magically made clickable:

https://example.com

visit: https://www.dreamwidth.org/beta to turn on the new "beta" better post editor