I agree it would be good to mark dead links, but we cannot edit our posts after a while so are unable to do it ourselves.
It could be something for the moderators to consider, but as they provide their services voluntarily and at no cost to us we cannot make hefty demands. We also appreciate the moderators' "hands off" approach and wouldn't want this to change.
In any case, one could also argue that there is no great harm in leaving the dead links: it is disappointing if you click on a dead link, but not the end of the world.
Perhaps this might put some newbie members off, but if they have the patience to work through the posts, they will find ample rewards.
Spike is right as ever ! We can't have access to our old post to modify the content or erase dead links.
The fact is all these posts are history now ; they are the witnesses of forum dynamics & activity ; i personally love explore old messages and remember debates or conversations we had in the past.
But if want something and link's dead, you can simply ask the original poster to repost, as a reply in original message, or in the topic dedicated to requests.