That's absolutely the case, and I'm sure it's more than a handful.

People create multiple reddit handles and use private VPN to ensure that each one logs in consistently from a unique IP address from the same location.

If someone is serious, or worse yet, funded, it's not hard to up and downvote a proportion of topics both in and outside of Bitcoin, and even make posts that look legitimate. Unless reddit wants to get into device fingerprinting (most of which doesn't work with javascript disabled) or has some way to do packet analysis, they can't tell either.

I imagine a lot of reddit's time is spent identifying patterns in these VPN sockpuppet bot accounts.

What I do personally? I look for the proportion of votes on a post relative to the other front page posts and see if they are in proportion to the number of comments in each, and if the comments are vapid (bots), or people passionately discussing something (more expensive to game).

The worst are the "First Last says X on Twitter" posts with 140 upvotes and zero comments. Those people are paying someone to upvote bot their posts.

Both /r/btc and /r/bitcoin have groups employing this tactic. I don't have hard evidence, but it's blatantly obvious if you carefully observe and approximate how the system works. It's really a bit of a propaganda shit show.