after `Phoenix.HTML.html_escape`, block quote doesn’t work

Yeah, that’s unfortunately true. I never use blockquotes in Markdown so I forgot that it uses > as the character to denote blockquotes. html_escape will convert those to > so the question is: does it make sense to correct this and possibly sacrifice a little safety? You could theoretically write some code that would convert the > back to >, which is clunky but should be safe enough, I suppose.