In my third comment to this Stack Overflow question, I put in (one explicit, manually formatted link) and two URLs to other SO questions. Since the amount of characters in a comment is quite limited, and since I had to squeeze three links into that comment, I shortened these links to https://stackoverflow.com/questions/<ID>. (One of them has a superfluous / at the end.)
For reasons I don't understand, markdown failed to turn them into links. Note that markdown did not fail on marking code.

I have checked both links to be valid by copy-pasting them into my browser's address bar. There's nothing wrong with them.
I have also tried these links in test comments (which I deleted afterwards), and they both work fine there. Another test revealed that the sentence that contains them ("I've tagged What is the member variables list after the colon in a constructor good for? and C++, What does the colon after a constructor mean? as c++-faq."), posted as its own comment, will have the URLs turned into links, too.

What could I have done wrong to make this fail?

  • 2
    Just a note, you can shorten the URL further by using stackoverflow.com/q/210616 Nov 17, 2010 at 12:00
  • @Barry: http://stackoverflow.com/q/210616: stackoverflow.com/q/210616. Thanks, I didn't know that!
    – sbi
    Nov 17, 2010 at 12:02
  • Wizz bang magical features strip out the www. gubbins for display purposes. Nov 17, 2010 at 12:04
  • 1
    @Barry: SO doesn't have www.
    – sbi
    Nov 17, 2010 at 12:13

1 Answer 1


By design. You can no longer mix raw and markdown URLs in the same comment.

Pick one way or the other per comment and stick to it.

With the recent addition of magic links, this was becoming unfeasible, hence we've spent some time to have a better way for fixing this vulnerability. So after the next build, multiple link styles in comments work again.

  • Thanks for pointing this out. Is there a rationale to this? Because, by default, I'd question a design decision that nobody is able to figure out for 13 hours until the site owner comes and explains it.
    – sbi
    Nov 18, 2010 at 8:27
  • @sbi there was an exploit based on inappropriate mixing of URL parsers. It's a really odd thing to do on top of that IMHO; what is the valid use case for mixing markup styles in a comment? Nov 18, 2010 at 8:30
  • I guess I can't argue with preventing exploits. :) Thanks for explaining!
    – sbi
    Nov 18, 2010 at 8:45

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