Occasionally on 4chan, one will make a post which will inspire others for years to come. These so called "epic threads" are usually put into the 4chan archive to be locked away and to remember.

Here is a link to the 4chan archive, note it is NSFW: 4chanarchive.org

When somebody notices an epic thread, there will most likely be at least one post in saying "posting in an epic thread."

The reason for this is to simply be remembered as part of history.

Another variation to this is "toasting in an epic bread."