Firefox [Greasemonkey] (https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/) (or Chrome [Tempermonkey] (https://chrome.google.com/webstore/detail/tampermonkey/dhdgffkkebhmkfjojejmpbldmpobfkfo)) userscript for bulk Google Code wiki comments removal. It's really helpfull if you have hundreds of outdated comments in wiki articles.
It adds delete all above link near familiar delete comment link. You need project editor permission and should logged in for bulk delete. Also you can install script directly from [userscripts.org] (http://userscripts.org/scripts/show/156366)
![Simple example] (http://i.imgur.com/qBaKm.jpg "Simple example")
Notice: in case Greasemonkey or Tempermonkey did not load Cleaner script properly you need to manually add user includes with URLs of pages you need to clean.