A few things to check for:

• Non-breaking text in the title, content, and comments should have no adverse effects on layout or functionality.
• Check the browser window / tab title.
• If you are a plugin or widget developer, check that this text does not break anything.

The following CSS properties will help you support non-breaking text.

-ms-word-wrap: break-word;
word-wrap: break-word;

Special characters in the post title have been known to cause issues with JavaScript when it is minified, especially in the admin when editing the post itself (ie. issues with metaboxes, media upload, etc.).

• The post title renders the word “with” in italics and the word “markup” in bold.
• The post title markup should be removed from the browser window / tab.

This is typically done by placing the permalink on the post date.