What does [-] mean? I've started seeing it next to comments

As announced on https://news.ycombinator.com/item?id=12073675, that sign means you can collapse comments in thread.

Have you tried clicking it? You should try and report back your results.

It is not very obvious that this is an active site on the page.

Why? If he is afraid that it is downvoting, and he has nothing to downvote ...

downvotes (edit: votes in general) are reversible now too.

Armed with that information, I will click around everything that catches my eye!

That's the true hacker spirit!

Used to close a comment thread for more user-friendly browsing

Thank you!

Title tag could clear most of confusion. Upvote has it.