A '\n' (newline) character is included at the end of every tag output by theme_html_tag(). This causes extra whitespace that may not always be desired. One specific example is for use with sprite icons that are included within links.
<a href="#"><span class="sprite"></span>Text</a>
If the span above is rendered using theme_html_tag() then there will be extra whitespace between the icon and the text because of the newline character. Any spacing would be better controlled by css (margin or padding).
FAILED: [[SimpleTest]]: [MySQL] Unable to apply patch newline-causes-unwanted-whitespace-1268180-6.patch. Unable to apply patch. See the log in the details link for more information.
FAILED: [[SimpleTest]]: [MySQL] 35,801 pass(es), 6 fail(s), and 0 exception(s).
FAILED: [[SimpleTest]]: [PHP 5.4 MySQL] Unable to apply patch remove-newlines-1268180-1.patch. Unable to apply patch. See the log in the details link for more information.