I've been seeing some old threads (1+ year) showing up as recent posts but when I look at the date on the last post in the thread it appears that it wasn't at all recent (e.g. this one).

Now I know I new here but it's driving me a bit nuts. I get ready to reply then realize that the person I'm replying to could be dead or worse. So what's going on? How do these seemingly random threads get revived without a recent addition?

one of two reasons, it's either a reply from an anon poster, or a moderator bump.

This happens sometimes, anonymous user will come along and read an entire section and post in the threads they like. they don't see the last date and will post in that thread anyway.

Isn't it better to post in an existing thread than to start a new one anyway? information may have changed, or new information may be available that wasn't before. Otherwise, I would just let it roll off your back

A Mod, with a wild gleam in his eye; "IT'S ALIVE!"

Ok, thanks. That and since an anonymous post won't actually appear for a while, makes sense.