I mean, here's a Slashdot thread from 2005 (https://web.archive.org/web/20020923232012/http://slashdot.org/articles/02/09/10/0517248.shtml?tid=134) from archive.org showing not only voting, but nested comments.

Slashdot's "voting" was a little less direct and focused on using what it called "moderation" to keep content on the site relevant. I found the write-up, still pretty much unchanged, here.

Here's a 2004 thread article from kos with straight up reddit-like voting, not only showing the cumulative score but the # of votes, too.

Reddit was founded in 2005.