[rirrirler]

As I understand it, HN itself automatically rewrites www.reddit.com to old.reddit.com in submitted links. This works for direct links to posts and comments, but not share links (containing "/s/" in the path) like the one for this post.

[SSLy]

the share /s/ links come from the new reddit, and are a sure way to spot someone using that interface instead of the proper one.

[thrdbndndn]

Ah thanks, I had no idea HN processes links. Sorry for assuming it was the OP.