One case I can think of is HTML must be allowed in comments for some WYSIWYG libraries that can't output Markdown/BBcode or WhateverMarkup. If most user of the website is using WYSIWYG with only selective few prefers plain text editing, the ideas in this article might make sense.
Though, instead of went through all the trouble, I'd rather force my users to use Markdown + wmd than trying to deal with HTML in comments.
Though, instead of went through all the trouble, I'd rather force my users to use Markdown + wmd than trying to deal with HTML in comments.