In this order:

• Fix it, if you can. You can't comment but you can edit...
  But just fix the link, don't add commentary to their post.
• Find somebody in General Chat who can leave a comment
• And if the whole answer hinges on that link working, flag it for a mod (or improve it, if you can).

In this order:

• Fix it, if you can. You can't comment but you can edit...
  But just fix the link, don't add commentary to their post.
• Find somebody in General Chat who can leave a comment
• And if the whole answer hinges on that link working, flag it for a mod (or improve it, if you can).