toBoolean to toBooleanStrict

lib/form/comment.js

@@ -8,5 +8,5 @@ module.exports = form(
   field('commentForm.revision_id').trim().required(),
   field('commentForm.comment').trim().required(),
   field('commentForm.comment_position').trim().toInt(),
-  field('commentForm.is_markdown').trim().toBoolean()
+  field('commentForm.is_markdown').trim().toBooleanStrict()
 );