After the edit window closes on a post/comment, we now timestamp posts/comments in the timechain using OpenTimestamps. The resulting proof allows stackers to know a piece of content is at least as old as the bitcoin block that it's in. While maybe not super or immediately useful for SN, it's pretty cool.
This only applies to content created from this point forward so long as it's a post or the child of a post that's been timestamped. We might at some point timestamp historical content but we don't yet. We also don't upgrade timestamps to be independently verifiable, instead relying on the calendars we submitted the hashes to.
How this works:
/otsto the item's path
We might at some point make it easier to see the ots info, but for now you'll need to do the url stuff.
Assuming the edit window on this post has closed, you can view the timestamp.