Exempt shortcode from wp_texturize bypassing function priority

A safeguard against plugins who choose to filter content with wp_texturize before either SH's parse_shortcodes or parse_shortcodes_comment fires thier filters.
Case in point: bbPress runs all of it's post types' content through wptexturize with a priority of 6
Fixing typo in comment block

Got a little underscore happy on the last commit
Small formatting & comment tweaks