One Crayon

If a post is saved with a <code></code> tag that is immediately followed by a common block-level element (like a header, div, paragraph, list, and so forth), then two linebreaks will be placed after the more tag to ensure that the block-level element is not automatically wrapped in paragraph tags by WordPress’ content parser.
There is absolutely no reason to install this plugin unless you are using an external editor and having your whitespace stripped out when you save your posts. If you are editing through the WordPress admin screen, then this plugin will be worthless because you can easily control where the <code></code> tag falls by hand.

Breathable More Tag

Ensure that the  tag has space to breathe if the following tag is block-level

Angelo Mandato

Do more with the read more (<code></code>) Tag. This plugin makes all links below the (<code></code>) tag include the rel=”nofollow” attribute.
This plugin is ideal for blog posts that want to organize untrusted links below the <code></code> tag. This has become very important since the recent Google penguin and panda search algorithm changes.

Do More

Do more with the &lt;!--more--&gt; Tag, make all links below the &lt;!--more--&gt; tag include the rel="nofollow" attribute.

Breathable More Tag vs Do More