for isMarkdown = false

lib/util/slack.js

@@ -86,7 +86,12 @@ module.exports = function(crowi) {
       body = body.substr(0, 2000) + '...';
     }
 
-    return convertMarkdownToMrkdwn(body);
+    if (comment.isMarkdown) {
+      return convertMarkdownToMrkdwn(body);
+    }
+    else {
+      return body;
+    }
   };
 
   const prepareSlackMessageForPage = function(page, user, channel, updateType, previousRevision) {