The long bar (beneath the upvote/downvote buttons) that shows what level the current comment is at collapses comments by clicking it. Very unintuitive, and I only found it by accident.

ah, thanks... but yes, very unintuitive.

I'm not seeing that in the images I've seen so far, got a link?

That would be a huge issue if they really did that. RES will probably step in and fix that.

You have to click the vertical line next to the comment which is a ridiculous change. The minus/plus signs were intuitive, now it's a line that switches to a plus sign.

I will disagree with this. Clicking on the bar has been part of the interface for some subreddits for a while now (though not many). I find it quite nice because if you are reading a deep thread and want to collapse to the next N levels up, then you don't have to carefully scroll up while watching the vertical bar to find the top comment in order to minimize that thread. This makes it very easy to skip to the next top-level comment when a topic has lots of comments.

I think the way it works is nice, and what you described is a good use for it. It could use some better UI to make it easier to discover. It didn't occur to me to hover over or click it because I thought it was merely an indicator.