An experimental textplug to give the feature-block-plugins branch optional full HTML5 compatibility.

HTML5.textplug.php

<?php

/**
 *  HTML5 textplug for textile
 *  ==========================
 *
 *  Makes use of the default block handler implementation. Override by editing this file if you so wish.
 *
 *  Usage
 *  -----
 *
 *  place "HTML5. On" (without the quotes & note the capitalisation) as the first line of your HTML5 document. Thereafter you should be able to use HTML5
 * throughout your document and have textile issue abbrs, instead of acronyms.
 */

Textile::RegisterBlockHandler( 'HTML5', '_textile_html5_block_handler' );
function _textile_html5_block_handler( $textile, $tag, $att, $atts, $ext, $cite, $o1, $o2, $content, $c2, $c1, $eat )
{
  if( $tag === 'HTML5' ) 
  {
    # Remap the now deprecated 'acronym' with 'abbr'...
    $textile->glyph_replace[6] = '<abbr title="$2">$1</abbr>';  # TODO Glyph indexing will need to be made semantic

    # No visible output from this blockhandler...
    $eat = true;
  }
  return array($o1, $o2, $content, $c2, $c1, $eat);
}

# None of the following (AFAIK) require special implementations so they use the default textile block implementation
# indicated by a null handler.
Textile::RegisterBlockHandler( 'nav',     null );
Textile::RegisterBlockHandler( 'section', null );
Textile::RegisterBlockHandler( 'aside',   null );
Textile::RegisterBlockHandler( 'detail',  null );
Textile::RegisterBlockHandler( 'header',  null );
Textile::RegisterBlockHandler( 'footer',  null );
Textile::RegisterBlockHandler( 'address', null );
Textile::RegisterBlockHandler( 'hgroup',  null );
Textile::RegisterBlockHandler( 'figure',  null );
Textile::RegisterBlockHandler( 'figcaption',  null );

# End of file.

Actually, an interface to the glyphs and spans would be better -- then core could change the implementation if needed.